- Better exception when the database isn't found. - Allow for "manual:" pseudo-scheme in downloadURL to signal that   the download should be done manually.
- Better exception when the database isn't found.
- Allow for "manual:" pseudo-scheme in downloadURL to signal that
  the download should be done manually.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator