hovac

Whenever I attempt to run my 1.12.2 mod with Mixins it errors and says > There are no mappings for MC 1.12.2 If I remove the mappings = "stable_39" it errors and says MISSING REPLACEMENT DATA FOR MAPPING_CHANNEL How can I fix this problem? I dont have it when I dont use Mixins Additional information: Gradle version: 4.9 ForgeGradle version: 2.1-SNAPSHOT build.gradle file: https://pastebin.com/67KE54WL