Fix scalar iloc rebase
 - [x] closes #15686
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master -u -- "*.py" | flake8 --diff``
 - [ ] whatsnew entry

This is just a rebased version of #15778 . I want to make sense of the tests which failed, and which work fine instead on my machine.

Notice that I'm also working on a [more complete approach](https://github.com/pandas-dev/pandas/pull/15778#issuecomment-288380312) to positional indexing, which will obsolete part of this PR, but that's going to take a while (and this PR, besides fixing the bug, is a step in that direction, since it rationalizes a bit positional indexing).
Wow. With #15778 , 2 circleci nodes out of 4 failed. Rebased, now only 1 fails. Trying a trivial rebase, just to be sure, sorry for the noise. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=h1) Report
> Merging [#17163](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/929c66fd74da221078a67ea7fd3dbcbe21d642e0?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `93.87%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17163/graphs/tree.svg?token=eZ4WkYLtcO&width=650&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17163      +/-   ##
==========================================
+ Coverage   90.99%      91%   +<.01%     
==========================================
  Files         162      162              
  Lines       49508    49528      +20     
==========================================
+ Hits        45052    45072      +20     
  Misses       4456     4456
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.78% <93.87%> (+0.02%)` | :arrow_up: |
| #single | `40.28% <79.59%> (-0.05%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexing.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhpbmcucHk=) | `94.05% <100%> (+0.1%)` | :arrow_up: |
| [pandas/core/dtypes/cast.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Nhc3QucHk=) | `87.52% <72.72%> (-0.3%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.66% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/internals.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzLnB5) | `94.03% <0%> (-0.02%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `95.03% <0%> (-0.01%)` | :arrow_down: |
| [pandas/io/formats/format.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZm9ybWF0LnB5) | `96.03% <0%> (-0.01%)` | :arrow_down: |
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `95.45% <0%> (-0.01%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.05% <0%> (+1.81%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17163?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/17163?src=pr&el=footer). Last update [929c66f...aeb8bf7](https://codecov.io/gh/pandas-dev/pandas/pull/17163?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/17163?src=pr&el=h1) Report
> Merging [#17163](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/7bef6d873b8af5ee0d35ba4b42c8a4775a6b3f24?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `93.87%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17163/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17163      +/-   ##
==========================================
- Coverage      91%   90.98%   -0.02%     
==========================================
  Files         162      162              
  Lines       49508    49538      +30     
==========================================
+ Hits        45055    45073      +18     
- Misses       4453     4465      +12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.76% <93.87%> (ø)` | :arrow_up: |
| #single | `40.29% <79.59%> (-0.04%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexing.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhpbmcucHk=) | `94.05% <100%> (+0.1%)` | :arrow_up: |
| [pandas/core/dtypes/cast.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Nhc3QucHk=) | `87.52% <72.72%> (-0.3%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.71% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17163?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/17163?src=pr&el=footer). Last update [7bef6d8...b8ee051](https://codecov.io/gh/pandas-dev/pandas/pull/17163?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 (The failing test will be solved by #17002 - will rebase then) Hello @toobaz! Thanks for updating the PR.







Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on August 09, 2017 at 09:49 Hours UTC > yeah I'd rather not introduce a 'temporary' fix.

OK, then never mind.