Use print_function

Python 3.x does not provide the print operator
anymore. Use the print function, which is available
via an extra import from __future__ for all Python
versions >= 2.6

Change-Id: Ief6b43e7862deb6d4c6401d530830fe59b89cd34
diff --git a/tempest/config.py b/tempest/config.py
index 8795b33..f6fd1d9 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -15,9 +15,12 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from __future__ import print_function
+
 import os
 import sys
 
+
 from oslo.config import cfg
 
 from tempest.common import log as logging
@@ -559,7 +562,7 @@
 
         if not os.path.exists(path):
             msg = "Config file %(path)s not found" % locals()
-            print >> sys.stderr, RuntimeError(msg)
+            print(RuntimeError(msg), file=sys.stderr)
         else:
             config_files.append(path)