catch exceptions in the server proc, to be able to kill the entire chain of running servers

tests/test_helper.tcl

@@ -92,4 +92,12 @@ proc main {} {
     cleanup
 }
 
-main
+if {[catch { main } err]} {
+    if {[string length $err] > 0} {
+        # only display error when not generated by the test suite
+        if {$err ne "exception"} {
+            puts $err
+        }
+        exit 1
+    }
+}