Index: Lib/unittest/loader.py
===================================================================
--- Lib/unittest/loader.py      (revision 79899)
+++ Lib/unittest/loader.py      (working copy)
@@ -8,6 +8,7 @@
 
 from functools import cmp_to_key as _CmpToKey
 from fnmatch import fnmatch
+from traceback import extract_tb
 
 from . import case, suite
 
@@ -91,8 +92,10 @@
                     module = __import__('.'.join(parts_copy))
                     break
                 except ImportError:
+                    tb = sys.exc_info()[2]
+                    raised_here = extract_tb(tb)[-1][2] == 'loadTestsFromName'
                     del parts_copy[-1]
-                    if not parts_copy:
+                    if not parts_copy or not raised_here:
                         raise
             parts = parts[1:]
         obj = module