Hi, the pastebin has expired and I don't know what email is the "previous email"
or the "previous example"; could you please add more info here?  Thanks, and
sorry about the delayed response.  (Priority was listed as "wish" rather than
"bug", so I didn't read it until all the "critical" and "bug" tickets were
handled first.)

Steps to re-create
 
* Set up an environment as per my previous email but without the egg installed
in site-packages.
* Delete the egg from the egg_repository so that the file we expect to see is
missing, but is still indicated in the html file which is used as the index of
the egg repository directory.
* Try to easy install the egg (as in previous example) and take note of the
exception raised.
 
My error is here:
http://pastebin.com/m36b84d95
 
I'm guessing that we get a zipimporterror because the stream returned by the URL
fetching fuction is obviously not zip data. However in this case might it be
more appropriate to raise DistributionNotFound or some kind of special exception
that more correctly describes this situation?