#23406: Migrations not found when only .pyc files are available (e.g. in a
frozen
environment)
-------------------------------------+-------------------------------------
Reporter: Daniel Menzel | Owner: Dan
| Watson
Type: Bug | Status: assigned
Component: Migrations | Version: 1.7
Severity: Normal | Resolution:
Keywords: migrations, .pyc, | Triage Stage: Ready for
frozen, cx_Freeze | checkin
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Tim Graham):
If third-party apps continue to support Python 2 until it's EOL in 2020,
then there's a possibility pyc files will be generated. If we revert
51673c146e48ff6230eace39bac18fd555607bee, then using a version of Django
that doesn't ignore pyc files will given an exception like `ImportError:
bad magic number in 'polls.migrations.0002_auto_20180312_1426':
b'\x03\xf3\r\n'` if a Python 2 pyc file is present. Manually removing pyc
files fixes that. If we decided to revert
51673c146e48ff6230eace39bac18fd555607bee for Django 2.1, I think it would
be useful to add a more helpful message about the magic number error
instructing the user to manually remove pyc files. I'm not sure if the
extra hassle in that use case is worth the trade off of supporting frozen
environments (assuming that Python 3 frozen environments generate pyc
files -- I'm not sure about this as I haven't used frozen environments
before).
By Django 3.1 (released August 2020), I think we can safely assume most
apps won't support Python 2, so we could revert the pyc ignoring in Django
without much concern. The `MIGRATIONS_INCLUDE_PYC` setting would allow
more easily using frozen environments in Django 2.1 (to be released August
2018), two years earlier than if we take the alternate route. Given the
problem is there since Django 1.7 (September 2014), I don't know if two
more years makes much difference.
--
Ticket URL: <https://code.djangoproject.com/ticket/23406#comment:34>
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