Add bintray availability check

.github/workflows/bintray.yml

@@ -26,6 +26,8 @@ jobs:
         run: ./gradlew clean
       - name: Gradle build
         run: ./gradlew build # if test's failed, don't publish
+      - name: Check keys
+        run: ./gradlew :mirai-core:ensureBintrayAvailable :mirai-core-qqandroid:ensureBintrayAvailable
       - name: Gradle :mirai-core:bintrayUpload
         run: ./gradlew :mirai-core:bintrayUpload -Dbintray_user=${{ secrets.BINTRAY_USER }} -Pbintray_user=${{ secrets.BINTRAY_USER }} -Dbintray_key=${{ secrets.BINTRAY_KEY }} -Pbintray_key=${{ secrets.BINTRAY_KEY }}
       - name: Gradle :mirai-core-qqandroid:bintrayUpload

gradle/publish.gradle

@@ -3,6 +3,11 @@ import upload.Bintray
 // 部分源码来自 kotlinx.coroutines
 // Source code from kotlinx.coroutines
 
+task ensureBintrayAvailable() {
+    if (!Bintray.isBintrayAvailable(project)) {
+        throw new IllegalStateException("bintray isn't available. ")
+    }
+}
 
 if (!Bintray.isBintrayAvailable(project)) {
     println("bintray isn't available. NO PUBLICATIONS WILL BE SET")