windows: degrade to py2 behavior when reading a non-symlink as a symlink While waiting for the push to hg-committed in WSL to complete, I ran a `phabimport` from Windows and got this traceback: $ hg phabimport 11313 ** Unknown exception encountered with possibly-broken third-party extension "mercurial_keyring" (version N/A) ** which supports versions unknown of Mercurial. ** Please disable "mercurial_keyring" and try your action again. ** If that fixes the bug please report it to https://foss.heptapod.net/mercurial/mercurial_keyring/issues ** Python 3.9.5 (default, May 6 2021, 17:29:31) [MSC v.1928 64 bit (AMD64)] ** Mercurial Distributed SCM (version 5.9rc1+hg32.0e2f5733563d) ** Extensions loaded: absorb, blackbox, evolve 10.3.3, extdiff, fastannotate, fix, mercurial_keyring, mq, phabblocker 20210126, phabricator, rebase, show, strip, topic 0.22.3 Traceback (most recent call last): File "mercurial.lock", line 279, in _trylock File "mercurial.vfs", line 202, in makelock File "mercurial.util", line 2147, in makelock FileExistsError: [WinError 183] Cannot create a file when that file already exists: b'hp-omen:78348' -> b'C:\\Users\\Matt\\hg/.hg/store/lock' During handling of the above exception, another exception occurred: Traceback (most recent call last): File "<string>", line 24, in <module> File "mercurial.dispatch", line 144, in run File "mercurial.dispatch", line 250, in dispatch File "mercurial.dispatch", line 294, in _rundispatch File "mercurial.dispatch", line 470, in _runcatch File "mercurial.dispatch", line 480, in _callcatch File "mercurial.scmutil", line 153, in callcatch File "mercurial.dispatch", line 460, in _runcatchfunc File "mercurial.dispatch", line 1273, in _dispatch File "mercurial.dispatch", line 918, in runcommand File "mercurial.dispatch", line 1285, in _runcommand File "mercurial.dispatch", line 1271, in <lambda> File "mercurial.util", line 1886, in check File "mercurial.util", line 1886, in check File "hgext.mq", line 4239, in mqcommand File "mercurial.util", line 1886, in check File "mercurial.util", line 1886, in check File "hgext.phabricator", line 314, in inner File "hgext.phabricator", line 2222, in phabimport File "hgext.phabricator", line 2123, in readpatch File "hgext.phabricator", line 2199, in _write File "mercurial.localrepo", line 2956, in lock File "mercurial.localrepo", line 2918, in _lock File "mercurial.lock", line 152, in trylock File "mercurial.lock", line 283, in _trylock File "mercurial.lock", line 314, in _readlock File "mercurial.vfs", line 221, in readlock File "mercurial.util", line 2163, in readlock File "mercurial.windows", line 619, in readlink ValueError: not a symbolic link Both exceptions look accurate (the file exists, and the Windows side can't read WSL side symlinks). I didn't try to reproduce this entirely within the Windows side, but we can do better than a cryptic stacktrace. With this change, the same scenario results in this abort: abort: C:\Users\Matt\hg/.hg/store/lock: The file cannot be accessed by the system When both the `push` and `phabimport` are done on the Windows side, it prints a message about waiting for the lock, and successfully applies the patch after the push completes. I'm not sure if there's enough info to be able to convert the abort into the wait scenario. As it stands now, we don't support symlinks on Windows, which requires either a UAC Administrator level process or an opt-in in developer mode, and there are several places where the new symlink on Windows support in py3 was explicitly disabled in order to get tests to pass quicker. Differential Revision: https://phab.mercurial-scm.org/D11333