print and exec have custom syntax error messages when using old syntax

[slide]

>>> print foo
  File "<stdin>", line 1
    print foo
            ^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print(foo)?

[slide]

>>> exec foo
  File "<stdin>", line 1
    exec foo
           ^
SyntaxError: Missing parentheses in call to 'exec'

[slide]

https://github.com/python/cpython/blob/43c0f1ac5ed8bc9c3bd048d2ce4de4c98a83de99/Objects/exceptions.c#L2893

[slozier]

There are tests for these in:

• test_grammar.test_former_statements_refer_to_builtins
• test_print.TestPy2MigrationHint (in 3.6)
• test_exceptions.testSyntaxErrorMissingParens (in 3.6)