'`brew_path` must be one of:
- None
- a string containing only:
- alphanumeric characters
- dashes
- dots
- spaces
- os.path.sep'

@classmethod
def valid_brew_path(cls, brew_path):

    if (brew_path is None):
        return True
    return (isinstance(brew_path, string_types) and (not cls.INVALID_BREW_PATH_REGEX.search(brew_path)))
