Add `dist` to the distribution map

def add(self, dist):
        """Add `dist` to the distribution map"""
        new_path = (
            dist.location not in self.paths and (
                dist.location not in self.sitedirs or
                # account for '.' being in PYTHONPATH
                dist.location == os.getcwd()
            )
        )
        if new_path:
            self.paths.append(dist.location)
            self.dirty = True
        Environment.add(self, dist)