gh-XXXXX: Fix pprint.isreadable() returning True for inf/nan

inf, -inf, nan are not valid Python literals so eval() fails on them.
isreadable() should return False for these values.

Author: stefanzetzsche

Lib/pprint.py

@@ -626,6 +626,10 @@ def _pprint_user_string(self, object, stream, indent, allowance, context, level)
     def _safe_repr(self, object, context, maxlevels, level):
         # Return triple (repr_string, isreadable, isrecursive).
         typ = type(object)
+        if typ is float:
+            import math
+            if math.isinf(object) or math.isnan(object):
+                return repr(object), False, False
         if typ in _builtin_scalars:
             return repr(object), True, False