Exit 1 on syntax test error

So the CI task fails.

.github/workflows/ci.yaml

@@ -13,7 +13,6 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
-  #fixme: it seems like syntax tests always pass?
   syntax_tests:
     name: Syntax tests
     runs-on: "ubuntu-latest"

tests/syntax.py

@@ -81,11 +81,13 @@
 signal_lines = [line for line in output.splitlines() if line != noise_line]
 
 last_line = signal_lines[-1]
-if last_line == "exiting with code 0":
-    # colorize last line in green
+success = last_line == "exiting with code 0"
+
+if success: # colorize last line in green
     signal_lines[-1] = f"\033[32m{last_line}\033[00m"
-else:
-    # colorize last line in red
+else: # colorize last line in red
     signal_lines[-1] = f"\033[31m{last_line}\033[00m"
-
 print("\n".join(signal_lines))
+
+if not success:
+    exit(1)