[IMP] core: reintroduce warning on watch

Was removed during the watch refactoring of #111422, present to avoid
people merging `watch=True`.

closes odoo/odoo#132727

X-original-commit: d2b33743e1b6faef82b24eb1e30b142e6b072290
Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>

odoo/tests/common.py

@@ -1745,6 +1745,9 @@ class HttpCase(TransactionCase):
         if any(f.filename.endswith('/coverage/execfile.py') for f in inspect.stack()  if f.filename):
             timeout = timeout * 1.5
 
+        if watch:
+            _logger.warning('watch mode is only suitable for local testing')
+
         browser = ChromeBrowser(type(self), headless=not watch)
         try:
             self.authenticate(login, login, browser=browser)