Change zope's classProvides to be a class decorator.

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

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

Following the listed advice seems to function in Python 3.

examples/plugins/letsencrypt_example_plugins.py

@@ -10,9 +10,9 @@ from letsencrypt.plugins import common
 
 
 @zope.interface.implementer(interfaces.IAuthenticator)
+@zope.interface.provider(interfaces.IPluginFactory)
 class Authenticator(common.Plugin):
     """Example Authenticator."""
-    zope.interface.classProvides(interfaces.IPluginFactory)
 
     description = "Example Authenticator plugin"
 
@@ -21,9 +21,9 @@ class Authenticator(common.Plugin):
 
 
 @zope.interface.implementer(interfaces.IInstaller)
+@zope.interface.provider(interfaces.IPluginFactory)
 class Installer(common.Plugin):
     """Example Installer."""
-    zope.interface.classProvides(interfaces.IPluginFactory)
 
     description = "Example Installer plugin"
 

letsencrypt-apache/letsencrypt_apache/configurator.py

@@ -61,6 +61,7 @@ logger = logging.getLogger(__name__)
 #     and load()
 
 @zope.interface.implementer(interfaces.IAuthenticator, interfaces.IInstaller)
+@zope.interface.provider(interfaces.IPluginFactory)
 class ApacheConfigurator(augeas_configurator.AugeasConfigurator):
     # pylint: disable=too-many-instance-attributes,too-many-public-methods
     """Apache configurator.
@@ -81,7 +82,6 @@ class ApacheConfigurator(augeas_configurator.AugeasConfigurator):
     :ivar dict assoc: Mapping between domains and vhosts
 
     """
-    zope.interface.classProvides(interfaces.IPluginFactory)
 
     description = "Apache Web Server - Alpha"
 

letsencrypt-nginx/letsencrypt_nginx/configurator.py

@@ -32,6 +32,7 @@ logger = logging.getLogger(__name__)
 
 
 @zope.interface.implementer(interfaces.IAuthenticator, interfaces.IInstaller)
+@zope.interface.provider(interfaces.IPluginFactory)
 class NginxConfigurator(common.Plugin):
     # pylint: disable=too-many-instance-attributes,too-many-public-methods
     """Nginx configurator.
@@ -53,7 +54,6 @@ class NginxConfigurator(common.Plugin):
     :ivar tup version: version of Nginx
 
     """
-    zope.interface.classProvides(interfaces.IPluginFactory)
 
     description = "Nginx Web Server - currently doesn't work"
 

letsencrypt/plugins/common.py

@@ -34,8 +34,8 @@ hostname_regex = re.compile(
 @zope.interface.implementer(interfaces.IPlugin)
 class Plugin(object):
     """Generic plugin."""
-    # classProvides is not inherited, subclasses must define it on their own
-    #zope.interface.classProvides(interfaces.IPluginFactory)
+    # provider is not inherited, subclasses must define it on their own
+    # @zope.interface.provider(interfaces.IPluginFactory)
 
     def __init__(self, config, name):
         self.config = config

letsencrypt/plugins/manual.py

@@ -24,6 +24,7 @@ logger = logging.getLogger(__name__)
 
 
 @zope.interface.implementer(interfaces.IAuthenticator)
+@zope.interface.provider(interfaces.IPluginFactory)
 class Authenticator(common.Plugin):
     """Manual Authenticator.
 
@@ -35,7 +36,6 @@ class Authenticator(common.Plugin):
     .. todo:: Support for `~.challenges.TLSSNI01`.
 
     """
-    zope.interface.classProvides(interfaces.IPluginFactory)
     hidden = True
 
     description = "Manually configure an HTTP server"

letsencrypt/plugins/null.py

@@ -12,9 +12,9 @@ logger = logging.getLogger(__name__)
 
 
 @zope.interface.implementer(interfaces.IInstaller)
+@zope.interface.provider(interfaces.IPluginFactory)
 class Installer(common.Plugin):
     """Null installer."""
-    zope.interface.classProvides(interfaces.IPluginFactory)
 
     description = "Null Installer"
     hidden = True

letsencrypt/plugins/standalone.py

@@ -136,6 +136,7 @@ def supported_challenges_validator(data):
 
 
 @zope.interface.implementer(interfaces.IAuthenticator)
+@zope.interface.provider(interfaces.IPluginFactory)
 class Authenticator(common.Plugin):
     """Standalone Authenticator.
 
@@ -144,7 +145,6 @@ class Authenticator(common.Plugin):
     challenges from the certificate authority. Therefore, it does not
     rely on any existing server program.
     """
-    zope.interface.classProvides(interfaces.IPluginFactory)
 
     description = "Automatically use a temporary webserver"
 

letsencrypt/plugins/webroot.py

@@ -18,9 +18,9 @@ logger = logging.getLogger(__name__)
 
 
 @zope.interface.implementer(interfaces.IAuthenticator)
+@zope.interface.provider(interfaces.IPluginFactory)
 class Authenticator(common.Plugin):
     """Webroot Authenticator."""
-    zope.interface.classProvides(interfaces.IPluginFactory)
 
     description = "Webroot Authenticator"