Return environment list of absolute path to their prefixes.

def get_envs(self, log=True):
        """Return environment list of absolute path to their prefixes."""
        if log:
            logger.debug('')
#        return self._call_and_parse(['info', '--json'],
#                                    callback=lambda o, e: o['envs'])
        envs = os.listdir(os.sep.join([self.ROOT_PREFIX, 'envs']))
        envs = [os.sep.join([self.ROOT_PREFIX, 'envs', i]) for i in envs]

        valid_envs = [e for e in envs if os.path.isdir(e) and
                      self.environment_exists(prefix=e)]

        return valid_envs