BUG: resample by BusinessHour raises ValueError
 - [x] closes #12351
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
 - [x] whatsnew entry

I've been away from this issue for a long time. Just made this PR again at PyCon 2017. Sorry for a long absence.
New test looks good, seems to have some style errors though:

```
pandas/tests/test_resample.py:2573:37: E128 continuation line under-indented for visual indent
pandas/tests/test_resample.py:2574:37: E128 continuation line under-indented for visual indent
pandas/tests/test_resample.py:2589:37: E128 continuation line under-indented for visual indent
pandas/tests/test_resample.py:2590:37: E128 continuation line under-indented for visual indent
pandas/tests/test_resample.py:2593:9: E303 too many blank lines (2)
````

Just need to add one more space, so that block lines up vertically. Also can remove the extra blank line on 2593. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16447?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@04356a8`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `50%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16447/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/16447?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #16447   +/-   ##
=========================================
  Coverage          ?   90.42%           
=========================================
  Files             ?      161           
  Lines             ?    51025           
  Branches          ?        0           
=========================================
  Hits              ?    46138           
  Misses            ?     4887           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.26% <50%> (?)` | |
| #single | `40.17% <25%> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16447?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/resample.py](https://codecov.io/gh/pandas-dev/pandas/pull/16447?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzYW1wbGUucHk=) | `95.75% <50%> (ø)` | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16447?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/16447?src=pr&el=footer). Last update [04356a8...f355763](https://codecov.io/gh/pandas-dev/pandas/pull/16447?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/16447?src=pr&el=h1) Report
> Merging [#16447](https://codecov.io/gh/pandas-dev/pandas/pull/16447?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/97ad3fb9c87226ad983267e2891dbbf68432b8ea?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `50%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16447/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/16447?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16447      +/-   ##
==========================================
- Coverage    90.4%    90.4%   -0.01%     
==========================================
  Files         161      161              
  Lines       51033    51035       +2     
==========================================
  Hits        46136    46136              
- Misses       4897     4899       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.23% <50%> (-0.01%)` | :arrow_down: |
| #single | `40.17% <25%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16447?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/resample.py](https://codecov.io/gh/pandas-dev/pandas/pull/16447?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzYW1wbGUucHk=) | `95.75% <50%> (-0.33%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16447?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/16447?src=pr&el=footer). Last update [97ad3fb...6f03530](https://codecov.io/gh/pandas-dev/pandas/pull/16447?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Thanks, @TomAugspurger I just cleaned up you mention. ;) if you want to try to generalize can have another look. closing. I think this needs a bit more generalization. If you want to continue, pls ping. I'd like to continue for this Oct. I have some time to do now. Where can I start with? re-open this issue? Would you guide me? @jreback   can you rebase & move notes to 0.22.0 closing as stale, but if you'd like to keep working, ping and we can reopen