Add timeout to lock wait

pytools/persistent_dict.py

@@ -108,6 +108,10 @@ class LockManager(CleanupBase):
                     from warnings import warn
                     warn("could not obtain lock--delete '%s' if necessary"
                             % self.lock_file)
+                if attempts > 3 * 60:
+                    raise RuntimeError("waited more than three minutes "
+                            "on the lock file '%s'"
+                            "--something is wrong" % self.lock_file)
 
             cleanup_m.register(self)