code: def attempt_dev_link_via_import(self, egg):
          
          try:
              imported = __import__(egg)
          except ImportError:
              self.logger.warn("Tried importing '%s', but that also didn't work.", egg)
              self.logger.debug("For reference, sys.path is %s", sys.path)
              return
          self.logger.info("Importing %s works, however", egg)
          try:
              probable_location = os.path.dirname(imported.__file__)
          except:  # Bare except
              self.logger.exception("Determining the location failed, however")
              return
          filesystem_egg_link = os.path.join(
              self.dev_egg_dir,
              '%s.egg-link' % egg)
          f = open(filesystem_egg_link, 'w')
          f.write(probable_location)
          f.close()
          self.logger.info('Using sysegg %s for %s', probable_location, egg)
          self.added.append(filesystem_egg_link)
          return True
docs: Create egg-link to FS location if an egg is found through importing.
  
          Sometimes an egg *is* installed, but without a proper egg-info file.
          So we attempt to import the egg in order to return a link anyway.
  
          TODO: currently it only works with simple package names like
          "psycopg2" and "mapnik".