os-rust/tests/rustdoc-ui/invalid-theme-name.stderr

error: invalid argument: "$DIR/invalid-theme-name.rs"
   |
   = help: arguments to --theme must have a .css extension
Give a better error when --theme is not a CSS file Before: ``` error: invalid argument: "bacon.toml" ``` After: ``` error: invalid argument: "bacon.toml" \| = help: arguments to --theme must be CSS files ``` 2021-03-31 10:27:01 -04:00			`error: invalid argument: "$DIR/invalid-theme-name.rs"`
			`\|`
			`= help: arguments to --theme must have a .css extension`