interfaces: make the `peer` mixin not a Protocol to fix Python 3.10 failures
I ran the Windows tests locally instead of waiting 2.5h for CI, and it works.
Interestingly, on Windows 11, it wants to drop all(?) of the (known-bad-output mmap windows !)
lines that were recently added to tests to pass on Windows 10. (These were related to not closing mmapped .hg/cache
files before trying to delete them.) That's unrelated to this change though.
Edited by Matt Harbison