Reword hint to make clear it's the whole project that has no "matchin…

…g distributions"

src/pip/_internal/resolution/resolvelib/factory.py

@@ -812,8 +812,8 @@ def describe_trigger(parent: Candidate) -> str:
             msg = (
                 msg
                 + "\n\n"
-                + "Additionally, some conflict causes have no "
-                + "available versions for your environment:"
+                + "Additionally, some projects in these conflicts have no "
+                + "matching distributions available for your environment:"
                 + "\n    "
                 + "\n    ".join(sorted(no_candidates))
             )

tests/functional/test_new_resolver_errors.py

@@ -187,7 +187,7 @@ def test_new_resolver_no_versions_available_hint(script: PipTestEnvironment) ->
 
     # Check that the new hint message is present
     assert (
-        "Additionally, some conflict causes have no "
-        "available versions for your environment:\n"
+        "Additionally, some projects in these conflicts have no "
+        "matching distributions available for your environment:\n"
         "    incompatible-dep\n" in result.stdout
     ), str(result)