code: def fetch(self, requirement, tmpdir, force_scan=False, source=False):
          
          dist = self.fetch_distribution(requirement, tmpdir, force_scan, source)
          if dist is not None:
              return dist.location
          return None
docs: Obtain a file suitable for fulfilling `requirement`
  
          DEPRECATED; use the ``fetch_distribution()`` method now instead.  For
          backward compatibility, this routine is identical but returns the
          ``location`` of the downloaded distribution instead of a distribution
          object.