Emit deprecation warnings for Zope interfaces (#8970)

* Monkeypatch certbot.interfaces module to warn about deprecations

* Ignore our own warning

* Fix type

* Add a changelog entry

certbot/CHANGELOG.md

@@ -10,7 +10,9 @@ Certbot adheres to [Semantic Versioning](https://semver.org/).
 
 ### Changed
 
-*
+* `zope` based interfaces in `certbot.interfaces` module are deprecated and will
+  be removed in a future release of Certbot. Any import of these interfaces will
+  emit a warning to prepare the transition for developers.
 
 ### Fixed
 

certbot/certbot/interfaces.py

@@ -2,9 +2,13 @@
 from abc import ABCMeta
 from abc import abstractmethod
 from argparse import ArgumentParser
+import sys
+from types import ModuleType
+from typing import cast
 from typing import Iterable
 from typing import List
 from typing import Optional
+import warnings
 
 import zope.interface
 
@@ -480,3 +484,36 @@ class RenewDeployer(metaclass=ABCMeta):
         :type lineage: RenewableCert
 
         """
+
+
+# This class takes a similar approach to the cryptography project to deprecate attributes
+# in public modules. See the _ModuleWithDeprecation class here:
+# https://github.com/pyca/cryptography/blob/91105952739442a74582d3e62b3d2111365b0dc7/src/cryptography/utils.py#L129
+class _ZopeInterfacesDeprecationModule:
+    """
+    Internal class delegating to a module, and displaying warnings when
+    attributes related to Zope interfaces are accessed.
+    """
+    def __init__(self, module):
+        self.__dict__['_module'] = module
+
+    def __getattr__(self, attr):
+        if attr in ('IConfig', 'IPlugin', 'IPluginFactory', 'IAuthenticator',
+                    'IInstaller', 'IDisplay', 'IReporter'):
+            warnings.warn('{0} attribute in certbot.interfaces module is deprecated '
+                          'and will be removed soon.'.format(attr),
+                          DeprecationWarning, stacklevel=2)
+        return getattr(self._module, attr)
+
+    def __setattr__(self, attr, value):  # pragma: no cover
+        setattr(self._module, attr, value)
+
+    def __delattr__(self, attr):  # pragma: no cover
+        delattr(self._module, attr)
+
+    def __dir__(self):  # pragma: no cover
+        return ['_module'] + dir(self._module)
+
+
+# Patching ourselves to warn about Zope interfaces deprecation and planned removal.
+sys.modules[__name__] = cast(ModuleType, _ZopeInterfacesDeprecationModule(sys.modules[__name__]))

pytest.ini

@@ -16,7 +16,10 @@
 # 2) An ImportWarning is raised with older versions of setuptools and
 #    zope.interface. See
 #    https://github.com/zopefoundation/zope.interface/issues/68 for more info.
+# 3) The deprecation warning raised when importing old Zope interfaces from
+#    the certbot.interfaces module.
 filterwarnings =
     error
     ignore:The external mock module:PendingDeprecationWarning
     ignore:.*zope. missing __init__:ImportWarning
+    ignore:.*attribute in certbot.interfaces module is deprecated:DeprecationWarning