Cannot doctest a SyntaxError

[rhettinger]

BPO	1009729
Nosy	@tim-one, @rhettinger

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2004-08-16.00:33:57.000>
created_at = <Date 2004-08-16.00:20:23.000>
labels = ['invalid', 'library']
title = 'Cannot doctest a SyntaxError'
updated_at = <Date 2004-08-16.00:33:57.000>
user = 'https://github.com/rhettinger'

bugs.python.org fields:

activity = <Date 2004-08-16.00:33:57.000>
actor = 'tim.peters'
assignee = 'edloper'
closed = True
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2004-08-16.00:20:23.000>
creator = 'rhettinger'
dependencies = []
files = []
hgrepos = []
issue_num = 1009729
keywords = []
message_count = 2.0
messages = ['22073', '22074']
nosy_count = 3.0
nosy_names = ['tim.peters', 'rhettinger', 'edloper']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1009729'
versions = []

[rhettinger]

Currently, doctests cannot be used to demonstrate or
test that misconstructions produce a syntax error. I'm
not certain, but I believe that case is trappable and
veriable.

The following is an actual use case for one of the
tests I would like to have in test.test_genexps.py:

Verify that parenthesis are required in a statement
>>> def f(n):
...     return i*i for i in xrange(n)
...
SyntaxError: invalid syntax

[tim-one]

Logged In: YES
user_id=31435

doctest has always been able to handle SyntaxError; e.g.,
see test_generators.py.

You need a "Traceback:" line too. This is explained in detail
in the current (CVS) doctest LaTeX docs.

For example, this spelling works fine as a doctest:

"""
>>> def f(n):
...     return i*i for i in xrange(n)
Traceback (most recent call last):
   ...
SyntaxError: invalid syntax
"""

You can take out the ellipsis between Traceback and
SyntaxError if you like. You can also keep your "extra"
sys.PS2 line if you like.