Bug: traceback of pylint on branch master

guoang

traceback detail:

2: 'check code'
1520427154 ['pyflakes', 'pep8', 'mccabe'] []
Error detected while processing function pymode#buffer_post_write[10]..pymode#lint#check:
line   11:
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/guoang/.vim/plugged/python-mode/pymode/lint.py", line 46, in code_check
    options.linters_params['pylint']['clear_cache'] = True
KeyError: 'pylint'

It happens when 'pylint' is not in g:pymode_lint_checkers, leads to code checking failure.