def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
def _safe_close(self, sess):
    """Closes a session without raising an exception.

    Just like sess.close() but ignores exceptions.

    Args:
      sess: A `Session`.
    """
    # pylint: disable=broad-except
    try:
      sess.close()
    except Exception:
      # Intentionally not logging to avoid user complaints that
      # they get cryptic errors.  We really do not care that Close
      # fails.
      pass
    # pylint: enable=broad-except