Support more debuggers for breakpoint

theano/tests/breakpoint.py

 from __future__ import absolute_import, print_function, division
 import numpy as np
-import pdb
+import imp
 
 import theano
 from theano.gof import Op, Apply
@@ -116,7 +116,16 @@ class PdbBreakpoint(Op):
             print("Their contents can be altered and, when execution")
             print("resumes, the updated values will be used.")
             print("-------------------------------------------------")
-            pdb.set_trace()
+
+            if imp.find_module('pudb'):
+                import pudb
+                pudb.set_trace()
+            elif imp.find_module('ipdb'):
+                import ipdb
+                ipdb.set_trace()
+            else:
+                import pdb
+                pdb.set_trace()
 
             # Take the new values in monitored, cast them back to their
             # original type and store them in the output_storage