Use pycodestyle instead of PEP8

PEP8 was renamed to pycodestyle; this issue explains why:
https://github.com/PyCQA/pycodestyle/issues/466

This commit changes our tests to use pycodestyle instead of pep8.

It also means:
- making a couple of whitespace changes to appease the linter
- disabling warnings for bare `Except`s (ie `Except` instead of `Except
  ValueError`) – this seems like a sensible thing to catch but I’m not
  going to make meaningful code changes in this commit

scripts/run_tests.sh

@@ -27,7 +27,7 @@ function display_result {
 if [[ -z "$VIRTUAL_ENV" ]] && [[ -d venv ]]; then
   source ./venv/bin/activate
 fi
-pep8 .
+pycodestyle .
 display_result $? 1 "Code style check"
 
 py.test --cov=app --cov-report=term-missing tests/ --junitxml=test_results.xml