Fix error in test suite startup with dotted import names.

Detected first on ubuntu 12.04, but the bug is generic, we just hadn't
seen it before.  Will push straight to master as this will begin
causing problems as more people upgrade.

IPython/utils/importstring.py

@@ -1,43 +1,47 b''
 # encoding: utf-8
 """
 A simple utility to import something by its string name.
 
 Authors:
 
 * Brian Granger
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Functions and classes
 #-----------------------------------------------------------------------------
 
 def import_item(name):
     """Import and return bar given the string foo.bar."""
     package = '.'.join(name.split('.')[0:-1])
     obj = name.split('.')[-1]
     
     # Note: the original code for this was the following.  We've left it
     # visible for now in case the new implementation shows any problems down
     # the road, to make it easier on anyone looking for a problem.  This code
     # should be removed once we're comfortable we didn't break anything.
     
     ## execString = 'from %s import %s' % (package, obj)
     ## try:
     ##     exec execString
     ## except SyntaxError:
     ##     raise ImportError("Invalid class specification: %s" % name)
     ## exec 'temp = %s' % obj
     ## return temp
 
     if package:
         module = __import__(package,fromlist=[obj])
-        return module.__dict__[obj]
+        try:
+            pak = module.__dict__[obj]
+        except KeyError:
+            raise ImportError('No module named %s' % obj)
+        return pak
     else:
         return __import__(obj)