Fix the homebrew module failing because of warnings

Instead of checking if there is an error message, which can also be a
warning, we now check the return code.

This commit fixes ansible-collections#8229 ansible-collections#7044

plugins/modules/homebrew.py

@@ -415,7 +415,7 @@ def _current_package_is_installed(self):
         if self.force_formula:
             cmd.append("--formula")
         rc, out, err = self.module.run_command(cmd)
-        if err:
+        if rc != 0:
             self.failed = True
             self.message = err.strip()
             raise HomebrewException(self.message)