Bug 1721291 - Report jsapi-tests failures with more than just the result code. r=jonco

Differential Revision: https://phabricator.services.mozilla.com/D120294

testing/mach_commands.py

@@ -176,7 +176,7 @@ class AddTest(MachCommandBase):
         doc=None,
         overwrite=False,
         editor=MISSING_ARG,
-        **kwargs
+        **kwargs,
     ):
         import addtest
         import io
@@ -464,7 +464,7 @@ class Test(MachCommandBase):
                 command_context._mach_context,
                 argv=extra_args,
                 test_objects=tests,
-                **kwargs
+                **kwargs,
             )
             if res:
                 status = res
@@ -683,7 +683,10 @@ class SpiderMonkeyTests(MachCommandBase):
         test_env = os.environ.copy()
         test_env["TOPSRCDIR"] = command_context.topsrcdir
 
-        return subprocess.call(jsapi_tests_cmd, env=test_env)
+        result = subprocess.call(jsapi_tests_cmd, env=test_env)
+        if result != 0:
+            print(f"jsapi-tests failed, exit code {result}")
+        return result
 
     def run_check_js_msg(self, command_context):
         import subprocess