reads a file and returns the defined __version__ value

def find_version(*paths):
    '''reads a file and returns the defined __version__ value'''
    version_match = re.search(r"^__version__ ?= ?['\"]([^'\"]*)['\"]",
                              read(*paths), re.M)
    if version_match:
        return version_match.group(1)
    raise RuntimeError("Unable to find version string.")