fix race condition in profiledir creation.

IPython/core/profiledir.py

@@ -24,6 +24,7 b' Authors:'
 import os
 import shutil
 import errno
+import time
 
 from IPython.config.configurable import LoggingConfigurable
 from IPython.utils.path import get_ipython_package_dir, expand_path
@@ -79,8 +80,16 b' class ProfileDir(LoggingConfigurable):'
         if self._location_isset:
             raise RuntimeError("Cannot set profile location more than once.")
         self._location_isset = True
-        if not os.path.isdir(new):
+        num_tries = 0
+        max_tries = 5
+        while not os.path.isdir(new):
+            try:
             os.makedirs(new)
+            except OSError:
+                if num_tries > max_tries:
+                    raise
+                num_tries += 1
+                time.sleep(0.5)
         
         # ensure config files exist:
         self.security_dir = os.path.join(new, self.security_dir_name)
@@ -270,5 +279,3 b' class ProfileDir(LoggingConfigurable):'
         if not os.path.isdir(profile_dir):
             raise ProfileDirError('Profile directory not found: %s' % profile_dir)
         return cls(location=profile_dir, config=config)
-
-