improve message when uitest crashes

add message about running specific sub-test

Change-Id: Id680825944ecfcba18ac8d310d1ce36dbfed859a
Reviewed-on: https://gerrit.libreoffice.org/53627Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

solenv/gbuild/uitest-failed-default.sh

@@ -11,9 +11,12 @@ cat << EOF
 
 Error: a unit test failed:
 
-To rerun just this failed test without all others, run:
+To rerun just this failed test without all others, use:
     make UITest_$2
 
+Or to run just a specific test case method, use:
+    make UITest_$2 UITEST_TEST_NAME="package.ClassName.methodName"
+
 Or to do interactive debugging, put a long sleep in the beginning of the .py
 uitest file, and attach gdb to the running soffice process.