lib2to3.pgen2.parse.ParseError is not roundtrip pickleable

[asottile]

BPO	35312
Nosy	@serhiy-storchaka, @asottile
PRs	bpo-35312: Make lib2to3.pgen2.parse.ParseError round-trip pickle-able #10710

^{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 2020-03-16.17:50:10.619>
created_at = <Date 2018-11-26.04:03:58.131>
labels = ['3.8', '3.7', 'library']
title = 'lib2to3.pgen2.parse.ParseError is not roundtrip pickleable'
updated_at = <Date 2020-03-16.17:50:10.619>
user = 'https://github.com/asottile'

bugs.python.org fields:

activity = <Date 2020-03-16.17:50:10.619>
actor = 'Anthony Sottile'
assignee = 'none'
closed = True
closed_date = <Date 2020-03-16.17:50:10.619>
closer = 'Anthony Sottile'
components = ['Library (Lib)']
creation = <Date 2018-11-26.04:03:58.131>
creator = 'Anthony Sottile'
dependencies = []
files = []
hgrepos = []
issue_num = 35312
keywords = ['patch']
message_count = 3.0
messages = ['330404', '330547', '332955']
nosy_count = 2.0
nosy_names = ['serhiy.storchaka', 'Anthony Sottile']
pr_nums = ['10710']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue35312'
versions = ['Python 3.7', 'Python 3.8']

[asottile]

related to https://bugs.python.org/issue35311

encountered here: https://gitlab.com/pycqa/flake8/issues/473

minimal reproduction:

class TestPickleableException(unittest.TestCase):
    def test_ParseError(self):
        err = ParseError('msg', 2, None, (1, 'context'))
        err2 = pickle.loads(pickle.dumps(err))
        self.assertEqual(vars(err), vars(err2))

======================================================================
ERROR: test_ParseError (lib2to3.tests.test_parser.TestPickleableException)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/home/asottile/workspace/cpython/Lib/lib2to3/tests/test_parser.py", line 628, in test_ParseError
    err2 = pickle.loads(pickle.dumps(err))
TypeError: __init__() missing 3 required positional arguments: 'type', 'value', and 'context'

[serhiy-storchaka]

New changeset c57e6e2 by Serhiy Storchaka (Anthony Sottile) in branch 'master':
bpo-35312: Make lib2to3.pgen2.parse.ParseError round-trip pickle-able. (GH-10710)
c57e6e2

[asottile]

Looks like this was merged and can be marked as resolved -- should this be backported to 3.7?