old sys.path_hooks importer does not work with Python 3.4.0rc1

[ynkdir]

BPO	20763
Nosy	@brettcannon, @larryhastings, @matejcik, @ericsnowcurrently, @1st1
Files	issue_20763.diff

^{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 = 'https://github.com/brettcannon'
closed_at = <Date 2014-02-26.23:29:34.862>
created_at = <Date 2014-02-25.03:36:04.270>
labels = ['release-blocker']
title = 'old sys.path_hooks importer does not work with Python 3.4.0rc1'
updated_at = <Date 2014-03-17.06:31:11.561>
user = 'https://bugs.python.org/ynkdir'

bugs.python.org fields:

activity = <Date 2014-03-17.06:31:11.561>
actor = 'python-dev'
assignee = 'brett.cannon'
closed = True
closed_date = <Date 2014-02-26.23:29:34.862>
closer = 'brett.cannon'
components = []
creation = <Date 2014-02-25.03:36:04.270>
creator = 'ynkdir'
dependencies = []
files = ['34225']
hgrepos = []
issue_num = 20763
keywords = ['patch']
message_count = 12.0
messages = ['212158', '212189', '212190', '212229', '212233', '212234', '212254', '212261', '212325', '212327', '212328', '213832']
nosy_count = 9.0
nosy_names = ['brett.cannon', 'larry', 'donmez', 'matejcik', 'Arfrever', 'ynkdir', 'python-dev', 'eric.snow', 'yselivanov']
pr_nums = []
priority = 'release blocker'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue20763'
versions = ['Python 3.4']

[ynkdir]

Steps to reproduce:

$ cat a.py
import sys

class MyFinder:
    def __init__(self, path):
        if path != "__myfinder__":
            raise ImportError()

    def find_module(self, fullname, path=None):
        return None

sys.path_hooks.append(MyFinder)
sys.path.insert(0, '__myfinder__')

import time
print('OK')

$ python3.3 -V
Python 3.3.2+

$ python3.3 a.py
OK

$ python3.4 -V
Python 3.4.0rc1

$ python3.4 a.py
Traceback (most recent call last):
  File "a.py", line 14, in <module>
    import time
ImportError: spec missing loader

On Ubuntu 13.10.
python3.3 is ubuntu's package.
python3.4.0rc1 is built by myself.

Vim's custom importer does not work for it.

[vim_dev] Problem with Python 3.4
https://groups.google.com/d/msg/vim_dev/RfuOG7_Jabs/h3YzLTsRgv0J

[brettcannon]

The problem is that the PEP-451 switch accidentally cut out compatibility code for PathEntryFinder.find_module() since Python 3.3 started the transition to find_loader(). Adding a bit of code to http://hg.python.org/cpython/file/8ac9c3754d33/Lib/importlib/_bootstrap.py#l1865 and a test will fix it.

[brettcannon]

I should also mention that subclassing importlib.abc.PathEntryFinder solves this coding problem.

[brettcannon]

I have a fix, I just need to create a test.

[brettcannon]

Fix and test is attached. Can someone review it so I can check it in and get a cherrypick?

[ericsnowcurrently]

LGTM

[ynkdir]

It works fine. Thank you!

[brettcannon]

I'll try to commit tonight then and request a cherrypick.

[python-dev]

New changeset 5dec1604322c by Brett Cannon in branch 'default':
Issue bpo-20763: Fix importlib.machinery.PathFinder to support
http://hg.python.org/cpython/rev/5dec1604322c

[brettcannon]

Committed for Larry to cherrypick into 3.4.0. No Misc/NEWS so that Larry doesn't have merge issues and since it will be covered by 3.4.0.

[brettcannon]

Cherrypick bug is http://bugs.python.org/issue20789

[python-dev]

New changeset 149be7000c11 by Brett Cannon in branch '3.4':
Issue bpo-20763: Fix importlib.machinery.PathFinder to support
http://hg.python.org/cpython/rev/149be7000c11