Tox doesn't pass OBJC_DISABLE_INITIALIZE_FORK_SAFETY for MacOS test uns

[Christopher Wilcox]

Mac requires that you specify export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

Tox needs to specify to pass the ENV for executions.

[Carlton Gibson]

Related to #27086. Going to accept as tox should run on a clean checkout.

[Dustin Harrison]

I was able to recreate this issue using MacOS Mojave 10.14.6, Python 3.7.3

Without OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES while the tests were running the following messages would occasionally be emitted and eventually the tests would hang:

[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called.
objc[40052]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.

After applying my PR (​https://github.com/django/django/pull/11830) and running:

export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES
tox

all tests pass and don't hang.

[Christopher Wilcox]

Thanks for confirming you are also seeing this Dustin. I also had a fix but was trying to find someone to verify it wasn't just better on my machine. ​https://github.com/django/django/pull/11835

[Carlton Gibson <carlton@…>]

In b0e92fb:

Fixed #30806 -- Prevented tox tests hanging on macOS.

MacOS users may need to set OBJC_DISABLE_INITIALIZE_FORK_SAFETY=TRUE
(#27086) to prevent tests from hanging. If set, also pass the environment
variable to tox.