GH-83901: Improve Signature.bind error message for missing keyword-only params

Lib/inspect.py

@@ -3114,8 +3114,12 @@ def _bind(self, args, kwargs, *, partial=False):
                             parameters_ex = (param,)
                             break
                         else:
-                            msg = 'missing a required argument: {arg!r}'
-                            msg = msg.format(arg=param.name)
+                            if param.kind == _KEYWORD_ONLY:
+                                argtype = ' keyword-only'
+                            else:
+                                argtype = ''
+                            msg = 'missing a required{argtype} argument: {arg!r}'
+                            msg = msg.format(arg=param.name, argtype=argtype)
                             raise TypeError(msg) from None
             else:
                 # We have a positional argument to process

Lib/test/test_inspect.py

@@ -3891,7 +3891,8 @@ def test(foo, *, bar):
             self.call(test, 1, bar=2, spam='ham')
 
         with self.assertRaisesRegex(TypeError,
-                                     "missing a required argument: 'bar'"):
+                                     "missing a required keyword-only "
+                                     "argument: 'bar'"):
             self.call(test, 1)
 
         def test(foo, *, bar, **bin):

Misc/NEWS.d/next/Library/2022-07-27-19-47-51.gh-issue-83901.OSw06c.rst

@@ -0,0 +1 @@
+Improve :meth:`Signature.bind <inspect.Signature.bind>` error message for missing keyword-only arguments.