Fix coverage failure due to configparser

We use virtualenv in our tests to be able to validate scaffolds, and
virtualenv requires configparser on Python 2.7, which is a backport of
the Python 3.8 version of the stdlib library.

This means our import never falls back to attempting to import
ConfigParser instead, thereby failing coverage.

pyramid/compat.py

@@ -194,7 +194,7 @@ def is_nonstr_iter(v):
 
 try:
     import configparser
-except ImportError:
+except ImportError:  # pragma: nocover (virtualenv pulls in configparser backport)
     import ConfigParser as configparser
 
 try: