Create a separate packages directory for running pub.

tools/remove_html_imports.py

+#!/usr/bin/env python
+# Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+'''Tool for removing dart:html and related imports from a library.
+
+Copy SOURCE to TARGET, removing any lines that import dart:html.
+
+Usage:
+  python tools/remove_html_imports.py SOURCE TARGET
+'''
+
+import os
+import re
+import shutil
+import sys
+
+HTML_IMPORT = re.compile(r'''^import ["']dart:(html|html_common|indexed_db'''
+                         r'''|js|svg|web_(audio|gl|sql))["'];$''',
+                         flags=re.MULTILINE)
+
+def main(argv):
+  source = argv[1]
+  target = argv[2]
+  shutil.rmtree(target)
+  shutil.copytree(source, target)
+
+  for root, subFolders, files in os.walk(target):
+    for path in files:
+      if not path.endswith('.dart'): next
+      with open(os.path.join(root, path), 'r+') as f:
+        contents = f.read()
+        f.seek(0)
+        f.truncate()
+        f.write(HTML_IMPORT.sub(r'// import "dart:\1";', contents))
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))