Fix DeprecationWarning in Python 3.7

[hugovk]

Running pytest on master with Python 3.7.0:

=============================================== test session starts ================================================
platform darwin -- Python 3.7.0, pytest-3.8.1, py-1.5.4, pluggy-0.7.1
...
================================================= warnings summary =================================================
/private/tmp/toolz/toolz/itertoolz.py:394: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated, and in 3.8 it will stop working
  if isinstance(seq, (tuple, list, collections.Sequence)):

-- Docs: https://docs.pytest.org/en/latest/warnings.html
====================================== 199 passed, 1 warnings in 8.34 seconds ======================================

No warning with this branch:

============================================ 199 passed in 7.91 seconds ============================================

Also Git ignore a file created when running tests to make sure it isn't committed by mistake.

[hugovk]

The build failed for Python 3 because it's set up to fail if coverage is less than 100% and Python 3 doesn't hit the except ImportError bit:

$ if [[ $TRAVIS_PYTHON_VERSION != pypy* ]]; then coverage report --show-missing --fail-under=100 ; fi
Name                          Stmts   Miss  Cover   Missing
-----------------------------------------------------------
toolz/__init__.py                11      0   100%
toolz/_signatures.py            148      0   100%
toolz/curried/__init__.py        47      0   100%
toolz/curried/exceptions.py       8      0   100%
toolz/curried/operator.py        12      0   100%
toolz/dicttoolz.py               85      0   100%
toolz/functoolz.py              373      0   100%
toolz/itertoolz.py              345      2    99%   14-16
toolz/recipes.py                 10      0   100%
toolz/sandbox/__init__.py         2      0   100%
toolz/sandbox/core.py            37      0   100%
toolz/sandbox/parallel.py        14      0   100%
toolz/utils.py                    7      0   100%
-----------------------------------------------------------
TOTAL                          1099      2    99%

try:
    # Python 3
    from collections.abc import Sequence
except ImportError:
    # Python 2.7
    from collections import Sequence

I've added a # pragma: no cover to prevent this:

try:
    # Python 3
    from collections.abc import Sequence
except ImportError:  # pragma: no cover
    # Python 2.7
    from collections import Sequence

[eriknw]

Instead of using try-except here, can we move these into the appropriate if PY3: else: blocks above?

btw, you can use # pragma: py2 no cover or # pragma: py3 no cover to only skip coverage if Python 2 or 3.

[hugovk]

Moved as part of a rebase to resolve conflicts!

Thanks, that's a good tip about # pragma: py2 no cover etc.

[groutr]

@eriknw, can this be merged?

[hugovk]

It's been about a year since the last release, do you have a rough idea when the next is due out?

https://github.com/pytoolz/toolz/releases

Thank you!