Replace ConfigParser with six.moves.configparser

ConfigParser is available in python2 but not in python3.
ref:http://www.diveintopython3.net/porting-code-to-python-3-with-2to3.html

Change-Id: I537a13a26aa3ab936ff23af1cf37a1a18baccd8e

tools/install_venv.py

@@ -18,10 +18,11 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import ConfigParser
 import os
 import sys
 
+from six.moves import configparser
+
 import install_venv_common as install_venv
 
 
@@ -57,7 +58,7 @@ def main(argv):
     pip_requires = os.path.join(root, 'requirements.txt')
     test_requires = os.path.join(root, 'test-requirements.txt')
     py_version = "python%s.%s" % (sys.version_info[0], sys.version_info[1])
-    setup_cfg = ConfigParser.ConfigParser()
+    setup_cfg = configparser.ConfigParser()
     setup_cfg.read('setup.cfg')
     project = setup_cfg.get('metadata', 'name')