Build error with Python 3.10

[faulesocke]

% ./mach bootstrap
Dependencies were already installed!
% ./mach build
Traceback (most recent call last):
  File "/home/socke/projects/servo/./mach", line 47, in <module>
    main(sys.argv)
  File "/home/socke/projects/servo/./mach", line 29, in main
    mach = mach_bootstrap.bootstrap(topdir)
  File "/home/socke/projects/servo/python/mach_bootstrap.py", line 306, in bootstrap
    import mach.main
  File "/home/socke/projects/servo/python/_virtualenv3.10/lib/python3.10/site-packages/mach/main.py", line 19, in <module>
    from collections import Iterable
ImportError: cannot import name 'Iterable' from 'collections' (/usr/lib/python3.10/collections/__init__.py)

OS: Void Linux x64 glibc

mach bootstrap successfully installed dependencies on the first run. Building does not work however, as you can see above.

Further down the line I also get an error deep inside mozjs_sys also related to Python 3.10: collections.Sequence was moved to collections.abc.Sequence in 3.10. This error occurred to me when I tried embedding servo into another project but I guess it will also occur after the above error is fixed.

[nobodywasishere]

This seems like a problem with the upstream package mach, which hasn't been updated with the latest version of mach in the Firefox source code, which (after a quick look) has fixes for these issues.

[jdm]

I asked whether the Firefox build developers could publish a new version, but they recommend vendoring the current package and cherry-picking/fixing whatever is blocking us. That's the path I intend to follow.

[jdm]

Once #28648 merges, we'll be able to apply any fixes necessary to support new python versions inside python/mach/mach.