Change zope's implements to be a class decorator.

When attempting to import any module that uses zope.interface.implements
in Python 3, a TypeError is raised; it reads:

    TypeError: Class advice impossible in Python3.  Use the @implementer
    class decorator instead.

Following the listed advice seems to function in Python 3.

letsencrypt-compatibility-test/letsencrypt_compatibility_test/configurators/apache/apache24.py

@@ -34,11 +34,10 @@ SHARED_MODULES = {
     "vhost_alias"}
 
 
+@zope.interface.implementer(interfaces.IConfiguratorProxy)
 class Proxy(apache_common.Proxy):
     """Wraps the ApacheConfigurator for Apache 2.4 tests"""
 
-    zope.interface.implements(interfaces.IConfiguratorProxy)
-
     def __init__(self, args):
         """Initializes the plugin with the given command line args"""
         super(Proxy, self).__init__(args)

letsencrypt-compatibility-test/letsencrypt_compatibility_test/configurators/apache/common.py

@@ -19,12 +19,11 @@ APACHE_VERSION_REGEX = re.compile(r"Apache/([0-9\.]*)", re.IGNORECASE)
 APACHE_COMMANDS = ["apachectl", "a2enmod", "a2dismod"]
 
 
+@zope.interface.implementer(interfaces.IConfiguratorProxy)
 class Proxy(configurators_common.Proxy):
     # pylint: disable=too-many-instance-attributes
     """A common base for Apache test configurators"""
 
-    zope.interface.implements(interfaces.IConfiguratorProxy)
-
     def __init__(self, args):
         """Initializes the plugin with the given command line args"""
         super(Proxy, self).__init__(args)

letsencrypt-compatibility-test/letsencrypt_compatibility_test/validator.py

@@ -12,10 +12,10 @@ from letsencrypt import interfaces
 logger = logging.getLogger(__name__)
 
 
+@zope.interface.implementer(interfaces.IValidator)
 class Validator(object):
     # pylint: disable=no-self-use
     """Collection of functions to test a live webserver's configuration"""
-    zope.interface.implements(interfaces.IValidator)
 
     def certificate(self, cert, name, alt_host=None, port=443):
         """Verifies the certificate presented at name is cert"""