As error logs are emitted often (they happen when Black's cache
directory is created after blib2to3 tries to write its cache) and cause
issues to be filed by users who think Black isn't working correctly.
These errors are expected for now and aren't a cause for concern so
let's remove them to stop worrying users (and new issues from being
opened). We can improve the blib2to3 caching mechanism to write its
cache at the end of a successful command line invocation later.
- when a trailing comma is specified in any bracket pair, that signals to Black
that this bracket pair needs to be always exploded, e.g. presented as "one
item per line";
- this causes some changes to previously formatted code that erroneously left
trailing commas embedded into single-line expressions;
- internally, Black needs to be able to identify trailing commas that it put
itself compared to pre-existing trailing commas. We do this by using/abusing
lib2to3's `was_checked` attribute. It's True for internally generated
trailing commas and False for pre-existing ones (in fact, for all
pre-existing leaves and nodes).
Fixes#1288
- Move black.py to src/black/__init__.py
- Have setuptools_scm make src/_black_version.py and exclude from git
- Move blackd.py to src/blackd/__init__.py
- Move blib2to3/ to src/
- Update `setup.py`
- Update unittests to pass
- Mostly path fixing + resolving
- Update CI
- pre-commit config
- appveyor + travis
Tested on my mac with python 3.7.5 via:
```
python3 -m venv /tmp/tb3
/tmp/tb3/bin/pip install --upgrade setuptools pip coverage pre-commit
/tmp/tb2/bin/pip install ~/repos/black/
cd ~/repos/black/
/tmp/tb2/bin/coverage run tests/test_black.py
/tmp/tb3/bin/pre-commit run -a
/tmp/tb3/bin/black --help
/tmp/tb3/bin/black ~/repos/ptr/ptr.py
```