If you have a conditional import like this :
@import "plugin:rocket.chat?://resources/css/Rocket.Chat";

The super dev mode renderer fails with this error:

Unable to compile the SASS file
[...]
Caused by: io.bit3.jsass.CompilationException: Error: java.net.URISyntaxException: Unable to resolve SASS import, no matching source found: plugin:rocket.chat?://resources/css/Rocket.Chat
java.lang.RuntimeException: java.net.URISyntaxException: Unable to resolve SASS import, no matching source found: plugin:rocket.chat?://resources/css/Rocket.Chat
at org.ametys.core.minimize.css.sass.AmetysScssImporter.apply(AmetysScssImporter.java:117)
at io.bit3.jsass.adapter.NativeImporterWrapper.apply(NativeImporterWrapper.java:39)