Fix test_issue_1667.py break.

The break is only under pypy3.{7,8,9,10} and was caused by the
prompt-toolkit 3.0.42 release today.

tests/integration/cli/commands/test_issue_1667.py

@@ -32,9 +32,11 @@ def test_interpreter_constraints_range_coverage(
     # type: (...) -> None
 
     # The traitlets 5.2.2 release breaks IPython.
+    # The prompt-toolkit 3.0.42 release breaks under pypy3.10.
     constraints = os.path.join(str(tmpdir), "constraints.txt")
     with open(constraints, "w") as fp:
         fp.write("traitlets<5.2.2\n")
+        fp.write("prompt-toolkit<3.0.42\n")
 
     # We lock with an unconstrained IPython requirement and we know IPython latest does not support
     # Python 3.7. If locking respects ICs it should not pick latest, but a version that supports at