Python3 error when running alembic upgrade head

[Marco Falcioni]

Hello,

we are moving to python3 and we ran into the error - is there anything we should do differently?

Thanks

Marco

(alembic==0.8.5)

INFO  [alembic.runtime.migration] Context impl MySQLImpl.

INFO  [alembic.runtime.migration] Will assume non-transactional DDL.

Traceback (most recent call last):

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/revision.py", line 349, in _revision_for_ident

    revision = self._revision_map[resolved_id]

KeyError: 52

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

  File "/Users/joe/venv/test_py3/bin/alembic", line 11, in <module>

    sys.exit(main())

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/config.py", line 479, in main

    CommandLine(prog=prog).main(argv=argv)

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/config.py", line 473, in main

    self.run_cmd(cfg, options)

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/config.py", line 456, in run_cmd

    **dict((k, getattr(options, k)) for k in kwarg)

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/command.py", line 174, in upgrade

    script.run_env()

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/base.py", line 397, in run_env

    util.load_python_file(self.dir, 'env.py')

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/util/pyfiles.py", line 81, in load_python_file

    module = load_module_py(module_id, path)

  File "_py3/lib/python3.5/site-packages/alembic/util/compat.py", line 68, in load_module_py

    module_id, path).load_module(module_id)

  File "<frozen importlib._bootstrap_external>", line 385, in _check_name_wrapper

  File "<frozen importlib._bootstrap_external>", line 806, in load_module

  File "<frozen importlib._bootstrap_external>", line 665, in load_module

  File "<frozen importlib._bootstrap>", line 268, in _load_module_shim

  File "<frozen importlib._bootstrap>", line 693, in _load

  File "<frozen importlib._bootstrap>", line 673, in _load_unlocked

  File "<frozen importlib._bootstrap_external>", line 662, in exec_module

  File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed

  File "legacy_schema/env.py", line 70, in <module>

    run_migrations_online()

  File "legacy_schema/env.py", line 63, in run_migrations_online

    context.run_migrations()

  File "<string>", line 8, in run_migrations

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/runtime/environment.py", line 797, in run_migrations

    self.get_context().run_migrations(**kw)

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/runtime/migration.py", line 303, in run_migrations

    for step in self._migrations_fn(heads, self):

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/command.py", line 163, in upgrade

    return script._upgrade_revs(revision, rev)

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/base.py", line 310, in _upgrade_revs

    revs = list(revs)

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/revision.py", line 610, in _iterate_revisions

    requested_lowers = self.get_revisions(lower)

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/revision.py", line 299, in get_revisions

    return sum([self.get_revisions(id_elem) for id_elem in id_], ())

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/revision.py", line 299, in <listcomp>

    return sum([self.get_revisions(id_elem) for id_elem in id_], ())

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/revision.py", line 304, in get_revisions

    for rev_id in resolved_id)

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/revision.py", line 304, in <genexpr>

    for rev_id in resolved_id)

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/revision.py", line 352, in _revision_for_ident

    revs = [x for x in self._revision_map

  File "/Users/joe/venv/test_py3/lib/python3.5/site-packages/alembic/script/revision.py", line 353, in <listcomp>

    if x and x.startswith(resolved_id)]

TypeError: startswith first arg must be str or a tuple of str, not int

[Mike Bayer]

do you have any integer values inside your version files for the value
of "down_revision", "revision", "branch_labels", or "depends_on"? that
would be the problem. Those must be strings.

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[Marco]

Hi Mike,

that put us on the right track - the reason was a stray "use_unicode=0" in the connection string as we are migrating from py2 to py3. The value in the alembic_version version_num was being returned as byte, which the code was interpreting as a tuple of integer values.

Thanks for the quick response!

Cheers

Marco

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