sage --package update: Display upstream URL and warn if upstream_url …

…pattern does not use the VERSION variable

build/sage_bootstrap/updater.py

@@ -69,8 +69,11 @@ def _update_version(self, new_version):
     def download_upstream(self, download_url=None):
         tarball = self.package.tarball
         if download_url is None:
+            pattern = self.package.tarball_upstream_url_pattern
+            if pattern and 'VERSION' not in pattern:
+                print('Warning: upstream_url pattern does not use the VERSION variable')
             download_url = self.package.tarball_upstream_url
         if download_url is None:
             raise ValueError("package has no default upstream_url pattern, download_url needed")
-        print('Downloading tarball to {0}'.format(tarball.upstream_fqn))
+        print('Downloading tarball from {0} to {1}'.format(download_url, tarball.upstream_fqn))
         Download(download_url, tarball.upstream_fqn).run()