def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def get_revision(cls, location, rev=None):
        if rev is None:
            rev = 'HEAD'
        current_rev = cls.run_command(
            ['rev-parse', rev],
            show_stdout=False,
            stdout_only=True,
            cwd=location,
        )
        return current_rev.strip()