Before:
  runtime ale_linters/python/pycodestyle.vim

After:
  call ale#linter#Reset()
  silent file something_else.py

Execute(The pycodestyle handler should parse output):
  AssertEqual
  \ [
  \   {
  \     'lnum': 8,
  \     'col': 3,
  \     'type': 'E',
  \     'text': 'SyntaxError: invalid syntax',
  \     'code': 'E999',
  \   },
  \   {
  \     'lnum': 69,
  \     'col': 11,
  \     'text': 'multiple imports on one line',
  \     'code': 'E401',
  \     'type': 'E',
  \     'sub_type': 'style',
  \   },
  \   {
  \     'lnum': 77,
  \     'col': 1,
  \     'text': 'expected 2 blank lines, found 1',
  \     'code': 'E302',
  \     'type': 'E',
  \     'sub_type': 'style',
  \   },
  \   {
  \     'lnum': 88,
  \     'col': 5,
  \     'text': 'expected 1 blank line, found 0',
  \     'code': 'E301',
  \     'type': 'E',
  \     'sub_type': 'style',
  \   },
  \   {
  \     'lnum': 222,
  \     'col': 34,
  \     'text': 'deprecated form of raising exception',
  \     'code': 'W602',
  \     'type': 'W',
  \     'sub_type': 'style',
  \   },
  \   {
  \     'lnum': 544,
  \     'col': 21,
  \     'text': '.has_key() is deprecated, use ''in''',
  \     'code': 'W601',
  \     'type': 'W',
  \     'sub_type': 'style',
  \   },
  \ ],
  \ ale_linters#python#pycodestyle#Handle(bufnr(''), [
  \   'stdin:8:3: E999 SyntaxError: invalid syntax',
  \   'stdin:69:11: E401 multiple imports on one line',
  \   'stdin:77:1: E302 expected 2 blank lines, found 1',
  \   'stdin:88:5: E301 expected 1 blank line, found 0',
  \   'stdin:222:34: W602 deprecated form of raising exception',
  \   'example.py:544:21: W601 .has_key() is deprecated, use ''in''',
  \ ])