Style consistency: don't end error messages with exclamation points.

lib/codegen/meta/cdsl/isa.py

@@ -54,7 +54,7 @@ class TargetISA(object):
         self._predicates = dict()  # type: Dict[PredKey, PredNode]
 
         assert InstructionGroup._current is None,\
-            "InstructionGroup {} is still open!"\
+            "InstructionGroup {} is still open"\
             .format(InstructionGroup._current.name)
 
     def __str__(self):

lib/codegen/meta/cdsl/typevar.py

@@ -231,7 +231,7 @@ class TypeSet(object):
     def __hash__(self):
         # type: () -> int
         h = hash(self.typeset_key())
-        assert h == getattr(self, 'prev_hash', h), "TypeSet changed!"
+        assert h == getattr(self, 'prev_hash', h), "TypeSet changed"
         self.prev_hash = h
         return h