SQLiteConnector crashes when Mercurial is 4.8rc0

[Jun Omae]

$ /dev/shm/hg4.8rc0/bin/pip list
Package       Version
------------- -------
Genshi        0.7.1
mercurial     4.8rc0
pip           18.1
pkg-resources 0.0.0
setuptools    40.5.0
Trac          1.0.17
wheel         0.32.2

$ /dev/shm/hg4.8rc0/bin/trac-admin /var/trac/1.0-sqlite
...

Trac [/var/trac/1.0-sqlite]> wiki list
2018-11-02 01:19:16,988 Trac[pool] ERROR: Exception caught on create
Traceback (most recent call last):
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/trac/db/pool.py", line 105, in get_cnx
    cnx = connector.get_connection(**kwargs)
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/trac/db/sqlite_backend.py", line 172, in get_connection
    self._version = get_pkginfo(sqlite).get(
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/trac/util/__init__.py", line 790, in get_pkginfo
    metadata = 'METADATA' if dist.has_metadata('METADATA') else 'PKG-INFO'
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/hgdemandimport/demandimportpy2.py", line 151, in __getattr__
    return getattr(self._module, attr)
AttributeError: 'module' object has no attribute 'has_metadata'
Error: Unable to get database connection within 0 seconds. (AttributeError: 'module' object has no attribute 'has_metadata')

(tweeted in ​https://twitter.com/shunichigoto/status/1058003791088365569)

[Jun Omae]

We expect a module instance is imported by import sqlite3 but a hgdemandimport instance is imported with Mercurial 4.8rc0.

Mercurial 4.8rc0

>>> from trac.env import Environment
>>> env = Environment('/var/trac/1.0-sqlite')
>>> env.db_query('SELECT * FROM system LIMIT 1')
AttributeError: 'module' object has no attribute 'has_metadata'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/trac/db/api.py", line 123, in execute
    with self as db:
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/trac/db/api.py", line 176, in __enter__
    db = self.dbmgr.get_connection(readonly=True)
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/trac/db/api.py", line 289, in get_connection
    db = self._cnx_pool.get_cnx(self.timeout or None)
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/trac/db/pool.py", line 216, in get_cnx
    return _backend.get_cnx(self._connector, self._kwargs, timeout)
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/trac/db/pool.py", line 137, in get_cnx
    raise TimeoutError(errmsg)
trac.db.pool.TimeoutError: Unable to get database connection within 0 seconds. (AttributeError: 'module' object has no attribute 'has_metadata')
>>> 
>>> from mercurial.util import version
>>> version()
'4.8rc0'
>>> import sqlite3
>>> type(sqlite3)
<class 'hgdemandimport.demandimportpy2._demandmod'>
>>> from trac.util import get_pkginfo
>>> get_pkginfo(sqlite3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/trac/util/__init__.py", line 790, in get_pkginfo
    metadata = 'METADATA' if dist.has_metadata('METADATA') else 'PKG-INFO'
  File "/dev/shm/hg4.8rc0/local/lib/python2.7/site-packages/hgdemandimport/demandimportpy2.py", line 151, in __getattr__
    return getattr(self._module, attr)
AttributeError: 'module' object has no attribute 'has_metadata'

Mercurial 4.7.2

>>> from trac.env import Environment
>>> env = Environment('/var/trac/1.0-sqlite')
>>> env.db_query('SELECT * FROM system LIMIT 1')
[(u'database_version', u'29')]
>>> 
>>> from mercurial.util import version
>>> version()
'4.7.2'
>>> import sqlite3
>>> sqlite3
<module 'sqlite3' from '/usr/lib/python2.7/sqlite3/__init__.pyc'>
>>> from trac.util import get_pkginfo
>>> get_pkginfo(sqlite3)
{}