To reproduce:

cros clean --cache
cros cidbcreds

Backtrace:

clean$bin/summarize_build_stats --past-week --report-file summary-email.html
summarize_build_stats: Unhandled exception:
Traceback (most recent call last):
  File "bin/summarize_build_stats", line 93, in <module>
    main()
  File "bin/summarize_build_stats", line 29, in main
    wrapper.DoMain()
  File "/usr/local/google/home/dgarrett/sand/clean/chromite/scripts/wrapper.py", line 164, in DoMain
    commandline.ScriptWrapperMain(FindTarget)
  File "/usr/local/google/home/dgarrett/sand/clean/chromite/lib/commandline.py", line 829, in ScriptWrapperMain
    ret = target(argv[1:])
  File "/usr/local/google/home/dgarrett/sand/clean/chromite/scripts/summarize_build_stats.py", line 778, in main
    credentials = cros_cidbcreds.CheckAndGetCIDBCreds()
  File "/usr/local/google/home/dgarrett/sand/clean/chromite/cli/cros/cros_cidbcreds.py", line 33, in CheckAndGetCIDBCreds
    with locking.FileLock(cidb_dir_lock).write_lock():
  File "/usr/local/google/home/dgarrett/sand/clean/chromite/lib/locking.py", line 162, in write_lock
    self._enforce_lock(fcntl.LOCK_EX, message)
  File "/usr/local/google/home/dgarrett/sand/clean/chromite/lib/locking.py", line 85, in _enforce_lock
    self.locking_mechanism(self.fd, flags|fcntl.LOCK_NB)
  File "/usr/local/google/home/dgarrett/sand/clean/chromite/lib/locking.py", line 71, in fd
    self._fd = self._GetFd()
  File "/usr/local/google/home/dgarrett/sand/clean/chromite/lib/locking.py", line 251, in _GetFd
    fd = os.open(self.path, os.W_OK|os.O_CREAT|cloexec, 0o666)
OSError: [Errno 2] No such file or directory: '/usr/local/google/home/dgarrett/sand/clean/.cache/cidb_creds.lock'