Introduced in:
https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/581268#message-8489bbf431bcfce14d2316bf1cdbb3dc86e286b9

bot_update has no .gclient file, but gets a spec passed. It writes the .gclient file at some point before gclient sync. But when this 'gclient recurse' runs, it's not written yet:
https://cs.chromium.org/chromium/src/third_party/depot_tools/recipes/recipe_modules/bot_update/resources/bot_update.py?q=bot_update.py&sq=package:chromium&dr&l=1143

It probably uses stale .gclient files from previous runs, which leads to problems when the file changes, e.g.:
https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Ftryserver.v8%2Fv8_linux64_msan_rel%2F222%2F%2B%2Frecipes%2Fsteps%2Fbot_update%2F0%2Fstdout

Output:
===Running /usr/bin/python -u /b/rr/tmpbfVWhs/rw/checkout/scripts/slave/.recipe_deps/depot_tools/gclient.py recurse -v git update-index --refresh===
In directory: /b/c/b/v8_linux64_msan_rel
Looking for .gclient starting from /b/c/b/v8_linux64_msan_rel
Traceback (most recent call last):
  File "/b/rr/tmpbfVWhs/rw/checkout/scripts/slave/.recipe_deps/depot_tools/gclient.py", line 2649, in <module>
    sys.exit(main(sys.argv[1:]))
  File "/b/rr/tmpbfVWhs/rw/checkout/scripts/slave/.recipe_deps/depot_tools/gclient.py", line 2635, in main
    return dispatcher.execute(OptionParser(), argv)
  File "/b/rr/tmpbfVWhs/rw/checkout/scripts/slave/.recipe_deps/depot_tools/subcommand.py", line 252, in execute
    return command(parser, args[1:])
  File "/b/rr/tmpbfVWhs/rw/checkout/scripts/slave/.recipe_deps/depot_tools/gclient.py", line 1715, in CMDrecurse
    return client.RunOnDeps('recurse', args, ignore_requirements=True,
AttributeError: 'NoneType' object has no attribute 'RunOnDeps'