Restore friendly error messages

Use --verbose if you really want a full traceback with your 'you made a
typo in an package ID' messages.

It would be better to do this based on exception types (i.e. our own
exceptions - MetadataException, BuildException, VCSException) would not
print a traceback, but unexpected exceptions would. But the types are
not available at the 'fdroid' level currently.

fdroidserver/metadata.py

@@ -23,13 +23,14 @@ import glob
 import cgi
 import logging
 
+srclibs = []
 
 class MetaDataException(Exception):
     def __init__(self, value):
         self.value = value
 
     def __str__(self):
-        return repr(self.value)
+        return self.value
 
 app_defaults = {
     'Name': None,