def find(self, req):
dist = self.by_key.get(req.key)<EOL>if dist is not None and dist not in req:<EOL><INDENT>raise VersionConflict(dist,req)     <EOL><DEDENT>else:<EOL><INDENT>return dist<EOL><DEDENT>
Find a distribution matching requirement `req`

        If there is an active distribution for the requested project, this
        returns it as long as it meets the version requirement specified by
        `req`.  But, if there is an active distribution for the project and it
        does *not* meet the `req` requirement, ``VersionConflict`` is raised.
        If there is no active distribution for the requested project, ``None``
        is returned.