fix gh-5388. Crash fix in theano.pp(). Make subtensor pp follow the new internal interface.

theano/tensor/subtensor.py

@@ -969,12 +969,15 @@ class SubtensorPrinter:
             inputs = list(r.owner.inputs)
             input = inputs.pop()
             sidxs = []
-            inbrack_pstate = pstate.clone(precedence=-1000)
+            old_precedence = getattr(pstate, 'precedence', None)
+            try:
+                pstate.precedence = -1000
+
                 for entry in idxs:
                     if isinstance(entry, integer_types):
                         sidxs.append(str(entry))
                     elif isinstance(entry, scal.Scalar):
-                    sidxs.append(inbrack_pstate.pprinter.process(inputs.pop()))
+                        sidxs.append(pstate.pprinter.process(inputs.pop()))
                     elif isinstance(entry, slice):
                         if entry.start is None or entry.start == 0:
                             msg1 = ""
@@ -992,10 +995,15 @@ class SubtensorPrinter:
                             msg3 = ":%s" % entry.step
 
                         sidxs.append("%s:%s%s" % (msg1, msg2, msg3))
-            return "%s[%s]" % (pstate.pprinter.process(
-                input,
-                pstate.clone(precedence=1000)),
-                ", ".join(sidxs))
+            finally:
+                pstate.precedence = old_precedence
+
+            try:
+                pstate.precedence = 1000
+                sub = pstate.pprinter.process(input, pstate)
+            finally:
+                pstate.precedence = old_precedence
+            return "%s[%s]" % (sub, ", ".join(sidxs))
         else:
             raise TypeError("Can only print Subtensor.")