id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
27436	migrations.test_commands.MakeMigrationsTests fail on Windows when run on a different drive than C:	Zbigniew Siciarz	Zbigniew Siciarz	"Some of the test cases in MakeMigrationsTests fail on Windows due to inability to find a relative path between files located on separate drives. 
The tests create a temporary migrations directory using `tempfile.mkdtemp`, which on Windows creates a directory under C:\Temp (or C:\Users\<username>\AppData\Local\Temp). 

If one clones Django source code to a drive other than C:, then the makemigrations command tests fail with an error like the following (Windows 7, Python 3.5.1):

{{{
ERROR: test_makemigrations_non_interactive_not_null_alteration (migrations.test_commands.MakeMigrationsTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""D:\dev\django\tests\migrations\test_commands.py"", line 834, in test_makemigrations_non_interactive_not_null_alteration
    call_command(""makemigrations"", ""migrations"", interactive=False, stdout=out)
  File ""d:\dev\django\django\core\management\__init__.py"", line 130, in call_command
    return command.execute(*args, **defaults)
  File ""d:\dev\django\django\core\management\base.py"", line 330, in execute
    output = self.handle(*args, **options)
  File ""d:\dev\django\django\core\management\commands\makemigrations.py"", line 193, in handle
    self.write_migration_files(changes)
  File ""d:\dev\django\django\core\management\commands\makemigrations.py"", line 211, in write_migration_files
    migration_string = os.path.relpath(writer.path)
  File ""D:\Miniconda3\lib\ntpath.py"", line 574, in relpath
    path_drive, start_drive))
ValueError: path is on mount 'C:', start on mount 'D:'
}}}

Since the value returned from `relpath` is used only for display and not for any I/O, I'd suggest catching this `ValueError` and using an absolute path in that case."	Bug	closed	Core (Management commands)	dev	Normal	fixed			Ready for checkin	1	0	0	0	0	0