TST: Avoid DeprecationWarnings

[jbrockmendel]

Avoid a boatload of these:

pandas/tests/plotting/test_frame.py::TestDataFramePlots::()::test_plot
  /home/travis/build/pandas-dev/pandas/pandas/core/indexes/multi.py:1556: DeprecationWarning: using a non-integer number instead of an integer will result in an error in the future
    if lab[key] == -1:

  /home/travis/build/pandas-dev/pandas/pandas/io/formats/style.py:1039: DeprecationWarning: In future, it will be an error for 'np.bool_' scalars to be interpreted as an index
    return css_bar(min(x, zero), max(x, zero), colors[x > zero])

pandas/tests/series/test_analytics.py::TestCategoricalSeriesAnalytics::()::test_drop_duplicates_categorical_non_bool[False-datetime64[D]]
  source:2442: DeprecationWarning: invalid escape sequence \(

That last one was a nice little adventure tracking down to pd.util.testing.

Does not silence these, as I'm not confident that is The Right Thing To Do:

pandas/tests/tslibs/test_parsing.py::TestGuessDatetimeFormat::()::test_guess_datetime_format_nopadding[2011-1-1 0:0:0-%Y-%m-%d %H:%M:%S]
  /home/travis/miniconda3/envs/pandas/lib/python3.6/site-packages/dateutil/parser/__init__.py:46: DeprecationWarning: _timelex is a private class and may break without warning, it will be moved and or renamed in future versions.
    warnings.warn(msg, DeprecationWarning)

Does not silence these, as I'm not sure how:

pandas/tests/io/test_sql.py::TestSQLiteAlchemyConn::()::test_read_table
  /home/travis/miniconda3/envs/pandas/lib/python3.6/site-packages/_pytest/fixtures.py:795: RemovedInPytest4Warning: Fixture setup_method called directly. Fixtures are not meant to be called directly, are created automatically when test functions request them as parameters. See https://docs.pytest.org/en/latest/fixture.html for more information.
    res = next(it)

[pep8speaks]

Hello @jbrockmendel! Thanks for submitting the PR.

• There are no PEP8 issues in the file pandas/core/indexes/base.py !

• There are no PEP8 issues in the file pandas/core/indexes/multi.py !

• There are no PEP8 issues in the file pandas/io/formats/style.py !

• There are no PEP8 issues in the file pandas/util/testing.py !

• Complete extra results for this file :

file_to_check.py:2442:-258: W605 invalid escape sequence '('
file_to_check.py:2442:-255: W605 invalid escape sequence ')'

---

[codecov]

Codecov Report

Merging #22646 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #22646      +/-   ##
==========================================
+ Coverage   92.17%   92.17%   +<.01%     
==========================================
  Files         169      169              
  Lines       50708    50715       +7     
==========================================
+ Hits        46740    46747       +7     
  Misses       3968     3968

Flag	Coverage Δ
#multiple	90.58% <100%> (ø)	⬆️
#single	42.35% <55.55%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/util/testing.py	85.96% <ø> (ø)	⬆️
pandas/io/formats/style.py	96.43% <100%> (ø)	⬆️
pandas/core/indexes/multi.py	95.41% <100%> (ø)	⬆️
pandas/core/common.py	97.39% <100%> (+0.05%)	⬆️
pandas/core/indexes/base.py	96.45% <100%> (ø)	⬆️

---

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[jreback]

we do this a number of times in the indexing code

i think we have a function

maybe_convert_to_int_indexer iirc

if not can u make one

[jbrockmendel]

Index._convert_scalar_indexer looks like a candidate; need to check where it is called.

[jbrockmendel]

I take it back. core.common is right next to is_bool_indexer is the place for this.

[jreback]

thanks! some more if you have a chance :>