try to make autojump more robust to concurrent uses over network filesystems

When your home is on a network filesytems, multiple shells can try
to write to the autojump store concurrently. The previous system was
a bit dangerous since the name of the temp file was always the same.
This should be better, since the different autojump instances should
all write to different temporaries, and only the atomic rename() should
be concurrent. Time will tell...

autojump

@@ -19,6 +19,7 @@ from __future__ import division
 import cPickle
 import getopt
 from sys import argv,exit,stderr
+from tempfile import NamedTemporaryFile
 import os
 import signal
 max_keyweight=1000
@@ -38,19 +39,19 @@ def dicadd(dic,key,increment=1):
     dic[key]=dic.get(key,0.)+increment
 
 def save(path_dict,dic_file):
-    f=open(dic_file+".tmp",'w')
+    f=NamedTemporaryFile(dir=config_dir,delete=False)
     cPickle.dump(path_dict,f,-1)
     f.flush()
     os.fsync(f)
     f.close()
-    try:
-        os.rename(dic_file+".tmp",dic_file) #cf. http://thunk.org/tytso/blog/2009/03/15/dont-fear-the-fsync/
-        import time #backup file
+    os.rename(f.name,dic_file) #cf. http://thunk.org/tytso/blog/2009/03/15/dont-fear-the-fsync/
+    try: #backup file
+        import time 
         if not os.path.exists(dic_file+".bak") or time.time()-os.path.getmtime(dic_file+".bak")>86400:
             import shutil
             shutil.copy(dic_file,dic_file+".bak")
-    except OSError:
-        pass #Fail quietly, this usually means a concurrent autojump process already did the job
+    except OSError, e:
+        print >> stderr, "Error while creating backup autojump file. (%s)" % e
 
 def forget(path_dict,dic_file):
     """Gradually forget about directories. Only call from the actual jump since it can take time"""