Seeing inconsistent bot_update failures with:

In directory: e:\b\s\w\ir\cache\builder\win
Looking for .gclient starting from e:\b\s\w\ir\cache\builder\win
/usr/bin/env: ‘python’: No such file or directory
Error: Command 'git cache unlock --cache-dir e:\\b\\s\\w\\ir\\cache\\git --force --all' returned non-zero exit status 127
Traceback (most recent call last):
  File "e:\b\s\w\ir\kitchen-checkout\scripts\slave\.recipe_deps\depot_tools\recipes\recipe_modules\bot_update\resources\bot_update.py", line 1173, in <module>
===Failed in 0.0 mins===
    sys.exit(main())
  File "e:\b\s\w\ir\kitchen-checkout\scripts\slave\.recipe_deps\depot_tools\recipes\recipe_modules\bot_update\resources\bot_update.py", line 1157, in main
    checkout(options, git_slns, specs, revisions, step_text, shallow)
  File "e:\b\s\w\ir\kitchen-checkout\scripts\slave\.recipe_deps\depot_tools\recipes\recipe_modules\bot_update\resources\bot_update.py", line 1067, in checkout
    gclient_output = ensure_checkout(**checkout_parameters)
  File "e:\b\s\w\ir\kitchen-checkout\scripts\slave\.recipe_deps\depot_tools\recipes\recipe_modules\bot_update\resources\bot_update.py", line 813, in ensure_checkout
    disable_syntax_validation)
  File "e:\b\s\w\ir\kitchen-checkout\scripts\slave\.recipe_deps\depot_tools\recipes\recipe_modules\bot_update\resources\bot_update.py", line 355, in gclient_sync
    raise GclientSyncFailed(e.message, e.code, e.output)
__main__.GclientSyncFailed: e:\b\s\w\ir\cipd_bin_packages\bin\python.exe -u e:\b\s\w\ir\kitchen-checkout\scripts\slave\.recipe_deps\depot_tools\gclient.py sync --verbose --reset --force --ignore_locks --output-json e:\b\s\w\ir\tmp\tmpic3ncy.json --nohooks --noprehooks --delete_unversioned_trees --break_repo_locks --revision src@unmanaged failed with code 1 in e:\b\s\w\ir\cache\builder\win.


Examples:
 - https://ci.chromium.org/swarming/task/388bd1cfa5d6e310?server=chromium-swarm.appspot.com
 - https://ci.chromium.org/swarming/task/388ab387d5030f10?server=chromium-swarm.appspot.com
 - https://ci.chromium.org/swarming/task/3889be6a01126910?server=chromium-swarm.appspot.com
 - https://ci.chromium.org/swarming/task/3889c3a28d02e710?server=chromium-swarm.appspot.com
 - https://ci.chromium.org/swarming/task/388b7099f957a110?server=chromium-swarm.appspot.com