fail more completely by deleting dbhash from sys.modules if bsddb can't be

loaded - prevents second import later from succeeding spuriously - mostly of
use in regression tests where the module might get imported more than once

Lib/dbhash.py

@@ -1,6 +1,12 @@
 """Provide a (g)dbm-compatible interface to bsdhash.hashopen."""
 
-import bsddb
+import sys
+try:
+    import bsddb
+except ImportError:
+    # prevent a second import of this module from spuriously succeeding
+    del sys.modules[__name__]
+    raise
 
 __all__ = ["error","open"]