Deprecate zope-interface support

It's a C-based dependency for a dozen of lines of code.

If there's interest, we can publish it as a separate package.

src/attr/validators.py

@@ -244,7 +244,17 @@ def provides(interface):
     :raises TypeError: With a human readable error message, the attribute
         (of type `attrs.Attribute`), the expected interface, and the
         value it got.
+
+    .. deprecated:: 23.1.0
     """
+    import warnings
+
+    warnings.warn(
+        "attrs's zope-interface support is deprecated and will be removed in, "
+        "or after, April 2024.",
+        DeprecationWarning,
+        stacklevel=2,
+    )
     return _ProvidesValidator(interface)
 
 

tests/test_validators.py

@@ -349,7 +349,9 @@ class C:
             def f(self):
                 pass
 
-        v = provides(ifoo)
+        with pytest.deprecated_call():
+            v = provides(ifoo)
+
         v(None, simple_attr("x"), C())
 
     def test_fail(self, ifoo):
@@ -359,9 +361,12 @@ def test_fail(self, ifoo):
         value = object()
         a = simple_attr("x")
 
-        v = provides(ifoo)
+        with pytest.deprecated_call():
+            v = provides(ifoo)
+
         with pytest.raises(TypeError) as e:
             v(None, a, value)
+
         assert (
             "'x' must provide {interface!r} which {value!r} doesn't.".format(
                 interface=ifoo, value=value
@@ -375,7 +380,9 @@ def test_repr(self, ifoo):
         """
         Returned validator has a useful `__repr__`.
         """
-        v = provides(ifoo)
+        with pytest.deprecated_call():
+            v = provides(ifoo)
+
         assert (
             "<provides validator for interface {interface!r}>".format(
                 interface=ifoo