Adding pre commit

[emarondan]

Adding config files first. If I get an OK I will proceed to execute the hooks on all the code and fix it to comply.

[codecov]

Codecov Report

Merging #220 (99bee2d) into master (1251f26) will not change coverage.
Report is 1 commits behind head on master.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #220   +/-   ##
=======================================
  Coverage   96.18%   96.18%           
=======================================
  Files           9        9           
  Lines         498      498           
  Branches       94       94           
=======================================
  Hits          479      479           
  Misses          9        9           
  Partials       10       10           

Files	Coverage Δ
w3lib/encoding.py	98.57% <100.00%> (ø)
w3lib/html.py	95.49% <100.00%> (ø)
w3lib/http.py	100.00% <100.00%> (ø)
w3lib/url.py	98.70% <100.00%> (ø)
w3lib/util.py	72.22% <100.00%> (ø)

[Gallaecio]

This change is breaking mypy, because mypy does not understand self.assert*.

If flake8 complains about asserts, I believe we need to disable that check for all files (we will also use asserts outside tests for mypy’s sake).

I am a bit puzzled because in Scrapy we use asserts often, but I see nothing about ignoring such an error in https://github.com/scrapy/scrapy/blob/master/.flake8 (the ignored errors seem unrelated).

[emarondan]

I made that change to avoid a bandit issue. It was something like:

>> Issue: [B101:assert_used] Use of assert detected. The enclosed code will be removed when compiling to optimised byte code.
   Severity: Low   Confidence: High
   CWE: CWE-703 (https://cwe.mitre.org/data/definitions/703.html)
   Location: tests/test_url.py:1063:8
   More Info: https://bandit.readthedocs.io/en/0.0.0/plugins/b101_assert_used.html

[Gallaecio]

Oh, there it is indeed!

[Gallaecio]

Excluding tests from bandit checks would also be useful in any repo.

[emarondan]

Done in 5390b23