generate random task db in tests

avoids potential conflict with simultaneous test runs

per review by @fperez

IPython/parallel/tests/test_db.py

@@ -38,6 +38,12 b' from IPython.zmq.session import Session'
 # TestCases
 #-------------------------------------------------------------------------------
 
+
+def setup():
+    global temp_db
+    temp_db = tempfile.NamedTemporaryFile(suffix='.db').name
+
+
 class TestDictBackend(TestCase):
     def setUp(self):
         self.session = Session()
@@ -189,7 +195,8 b' class TestSQLiteBackend(TestDictBackend):'
 
     @dec.skip_without('sqlite3')
     def create_db(self):
-        return SQLiteDB(location=tempfile.gettempdir())
+        location, fname = os.path.split(temp_db)
+        return SQLiteDB(location=location, fname=fname)
     
     def tearDown(self):
         self.db._db.close()
@@ -198,6 +205,6 b' class TestSQLiteBackend(TestDictBackend):'
 def teardown():
     """cleanup task db file after all tests have run"""
     try:
-        os.remove(os.path.join(tempfile.gettempdir(), 'tasks.db'))
+        os.remove(temp_db)
     except:
         pass