Improve error message in GACT

Author: gsmet

independent-projects/bootstrap/app-model/src/main/java/io/quarkus/maven/dependency/GACT.java

@@ -66,8 +66,9 @@ public GACT(String groupId, String artifactId, String classifier, String type) {
     public static String[] split(String str, String[] parts, int fromIndex) {
         int i = str.lastIndexOf(':', fromIndex - 1);
         if (i <= 0) {
-            throw new IllegalArgumentException("For " + str + " groupId and artifactId separating ':' is absent or not in the right place in '"
-                    + str.substring(0, fromIndex) + "' at index " + fromIndex);
+            throw new IllegalArgumentException("Invalid coordinates '" + str
+                    + "': groupId and artifactId separating character ':' is absent or not in the right place in the substring ending at index "
+                    + fromIndex + ": '" + str.substring(0, fromIndex));
         }
         parts[3] = str.substring(i + 1, fromIndex);
         fromIndex = i;