ImportError: cannot import name getargspec

The author of the decorator module pushed a new version to PyPI a few days ago which removed functionality from the module without updating the major version. This means that decorator 4.3.0 will not work with Hail 0.1.

To fix this, use:

pip install decorator==4.2.1

An update: Current Hail 0.2 is compatible with later versions of decorator