CI: Exclude asv benchmark envs from flake8 checks

[qwhelan]

When running ci/code_checks.sh on a local repository that has also been used to run asv benchmarks, flake8 also lints the environments created. This massively increases the runtime and leads to linting errors on non-pandas packages, which is not informative.

This change simply adds env to the flake8 exclude list, which resolves the issue seen above.

Before

~/projects/pandas$ LINT=true ./ci/code_checks.sh
inside ./ci/code_checks.sh

flake8 --version
3.6.0 (mccabe: 0.6.1, pycodestyle: 2.4.0, pyflakes: 2.0.0) CPython 3.6.5 on Linux
Linting .py code
./asv_bench/env/83b3be1235aa7b08e8a17448e2f70790/bin/runxlrd.py:18:80: E501 line too long (80 > 79 characters)
./asv_bench/env/83b3be1235aa7b08e8a17448e2f70790/bin/runxlrd.py:38:15: E401 multiple imports on one line
./asv_bench/env/83b3be1235aa7b08e8a17448e2f70790/bin/runxlrd.py:43:5: E303 too many blank lines (2)
./asv_bench/env/83b3be1235aa7b08e8a17448e2f70790/bin/runxlrd.py:65:24: E701 multiple statements on one line (colon)
./asv_bench/env/83b3be1235aa7b08e8a17448e2f70790/bin/runxlrd.py:66:19: E701 multiple statements on one line (colon)
./asv_bench/env/83b3be1235aa7b08e8a17448e2f70790/bin/runxlrd.py:71:25: E128 continuation line under-indented for visual indent
...

After

~/projects/pandas$ LINT=true ./ci/code_checks.sh
inside ./ci/code_checks.sh

flake8 --version
3.6.0 (mccabe: 0.6.1, pycodestyle: 2.4.0, pyflakes: 2.0.0) CPython 3.6.5 on Linux
Linting .py code
./versioneer.py:423:1: E305 expected 2 blank lines after class or function definition, found 1
./versioneer.py:467:1: E305 expected 2 blank lines after class or function definition, found 0
./versioneer.py:927:-11937: W605 invalid escape sequence '\s'

Output comparison

~/projects/pandas$ ls -altrh code_check*
-rw-rw-rw- 1 chris chris 32M Nov  4 12:31 code_check_old.log
-rw-rw-rw- 1 chris chris 14K Nov  4 12:33 code_check_new.log

[jreback]

can u move these to the setup.cfg section instead

[qwhelan]

@jreback Done

[codecov]

Codecov Report

Merging #23497 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #23497   +/-   ##
=======================================
  Coverage   92.23%   92.23%           
=======================================
  Files         161      161           
  Lines       51197    51197           
=======================================
  Hits        47220    47220           
  Misses       3977     3977

Flag	Coverage Δ
#multiple	90.61% <ø> (ø)	⬆️
#single	42.27% <ø> (ø)	⬆️

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[datapythonista]

lgtm

You could add a comment too, something like env # directory created by asv after a run. Not being in the repo, we may have the temptation to delete it later on

[qwhelan]

@datapythonista Done

[jreback]

thanks @qwhelan