How to find out whether subversion working directory is locked by svn?

if os.path.isdir(checkout_dir):
     # working copy dir already exists
     return checkout_dir

checked-out failed: svn: Working copy '/tmp/qm_23683' locked
svn: run 'svn cleanup' to remove locks (type 'svn help cleanup' for details)**

import os, errno

# ...

try:
  os.mkdir(dirName)
except OSError, e:
  if e.errno != errno.EEXIST: raise # some other error
  print 'Directory already exists.'
else:
  print 'Successfully created new directory.'