Add some helpful messages to coverage script

.gitea/scripts/coverage.py

@@ -1,12 +1,17 @@
 import argparse
 import json
+import sys
 
 
 def main(coverage_file, fail_under):
     with open(coverage_file, encoding="utf-8") as f:
         coverage_json = json.load(f)
     coverage = float(coverage_json["message"][:-1])
-    return coverage >= fail_under
+    print(f"Code coverage: {coverage:.2f}%; Threshold: {fail_under:.2f}%")
+    success = coverage >= fail_under
+    if coverage < fail_under:
+        print("Insufficient code coverage", file=sys.stderr)
+    return success
 
 
 if __name__ == "__main__":