Added log10 to the list of unary functions df.eval can handle
- [x] closes https://github.com/pandas-dev/pandas/issues/24139 
- [x] tests ~~added~~ / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

`(pandas) ➜  pandas git:(binary_math_log) git diff upstream/master -u -- "*.py" | flake8 --diff
`
- [ ] whatsnew entry


Hello @euri10! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/computation/ops.py`](https://github.com/euri10/pandas/blob/5f46a28f918422b3199626becbaee561d22921c6/pandas/core/computation/ops.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=h1) Report
> Merging [#24140](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/03134cb92ed61d073438daac7a7c2a0e094efede?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24140/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24140   +/-   ##
=======================================
  Coverage    92.2%    92.2%           
=======================================
  Files         162      162           
  Lines       51701    51701           
=======================================
  Hits        47671    47671           
  Misses       4030     4030
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <ø> (ø)` | :arrow_up: |
| #single | `43.02% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vb3BzLnB5) | `95.6% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=footer). Last update [03134cb...8ecf4ce](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=h1) Report
> Merging [#24140](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/03134cb92ed61d073438daac7a7c2a0e094efede?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24140/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24140   +/-   ##
=======================================
  Coverage    92.2%    92.2%           
=======================================
  Files         162      162           
  Lines       51701    51701           
=======================================
  Hits        47671    47671           
  Misses       4030     4030
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <ø> (ø)` | :arrow_up: |
| #single | `43.02% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vb3BzLnB5) | `95.6% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=footer). Last update [03134cb...8ecf4ce](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=h1) Report
> Merging [#24140](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/03134cb92ed61d073438daac7a7c2a0e094efede?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24140/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24140   +/-   ##
=======================================
  Coverage    92.2%    92.2%           
=======================================
  Files         162      162           
  Lines       51701    51701           
=======================================
  Hits        47671    47671           
  Misses       4030     4030
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <ø> (ø)` | :arrow_up: |
| #single | `43.02% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vb3BzLnB5) | `95.6% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=footer). Last update [03134cb...8ecf4ce](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=h1) Report
> Merging [#24140](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/03134cb92ed61d073438daac7a7c2a0e094efede?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24140/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24140   +/-   ##
=======================================
  Coverage    92.2%    92.2%           
=======================================
  Files         162      162           
  Lines       51701    51701           
=======================================
  Hits        47671    47671           
  Misses       4030     4030
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <ø> (ø)` | :arrow_up: |
| #single | `43.02% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vb3BzLnB5) | `95.6% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=footer). Last update [03134cb...8ecf4ce](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=h1) Report
> Merging [#24140](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/03134cb92ed61d073438daac7a7c2a0e094efede?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24140/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24140   +/-   ##
=======================================
  Coverage    92.2%    92.2%           
=======================================
  Files         162      162           
  Lines       51701    51701           
=======================================
  Hits        47671    47671           
  Misses       4030     4030
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <ø> (ø)` | :arrow_up: |
| #single | `43.02% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vb3BzLnB5) | `95.6% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=footer). Last update [03134cb...8ecf4ce](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=h1) Report
> Merging [#24140](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/03134cb92ed61d073438daac7a7c2a0e094efede?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24140/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24140      +/-   ##
==========================================
+ Coverage    92.2%   92.21%   +<.01%     
==========================================
  Files         162      162              
  Lines       51701    51723      +22     
==========================================
+ Hits        47671    47695      +24     
+ Misses       4030     4028       -2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.61% <ø> (ø)` | :arrow_up: |
| #single | `43.03% <ø> (+0.01%)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vb3BzLnB5) | `95.6% <ø> (ø)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.41% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `93.67% <0%> (-0.05%)` | :arrow_down: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.27% <0%> (-0.01%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.91% <0%> (ø)` | :arrow_up: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.65% <0%> (ø)` | :arrow_up: |
| [pandas/core/arrays/interval.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2ludGVydmFsLnB5) | `92.98% <0%> (ø)` | :arrow_up: |
| [pandas/core/groupby/groupby.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9ncm91cGJ5LnB5) | `96.5% <0%> (ø)` | :arrow_up: |
| [pandas/io/pytables.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3B5dGFibGVzLnB5) | `92.31% <0%> (ø)` | :arrow_up: |
| [pandas/core/internals/managers.py](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL21hbmFnZXJzLnB5) | `95.93% <0%> (+0.01%)` | :arrow_up: |
| ... and [5 more](https://codecov.io/gh/pandas-dev/pandas/pull/24140/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=footer). Last update [03134cb...068b474](https://codecov.io/gh/pandas-dev/pandas/pull/24140?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 can you add a test for this, in pandas/tests/computation/test_eval.py & a whatsnew note (bug fixes for numeric is ok) Added the whatsnew part as requested @jreback 
For the tests, it seems unecessary to me to add something new, the existing one are already handled  in [here](https://github.com/pandas-dev/pandas/blob/master/pandas/tests/computation/test_eval.py#L1625-L1633) by looping through `unary_fns` which get its value from `_unary_math_ops` I just extended.
  lgtm ping on green.