yanglint BUGFIX debug tests

Now they shouldn't be skipping anymore.
diff --git a/tools/lint/tests/interactive/debug.test b/tools/lint/tests/interactive/debug.test
index d04c0f0..8a64c92 100644
--- a/tools/lint/tests/interactive/debug.test
+++ b/tools/lint/tests/interactive/debug.test
@@ -3,28 +3,28 @@
 set mdir $::env(YANG_MODULES_DIR)
 
 test debug_dict {Check debug message DICT} {
--setup $ly_setup -cleanup $ly_cleanup -constraints {[ly_cmd_exists "debug"]} -body {
+-setup $ly_setup -cleanup $ly_cleanup -constraints {[yanglint_debug]} -body {
     ly_cmd "verb debug"
     ly_cmd "debug dict"
     ly_cmd "load modleaf" "DICT"
 }}
 
 test debug_xpath {Check debug message XPATH} {
--setup $ly_setup -cleanup $ly_cleanup -constraints {[ly_cmd_exists "debug"]} -body {
+-setup $ly_setup -cleanup $ly_cleanup -constraints {[yanglint_debug]} -body {
     ly_cmd "verb debug"
     ly_cmd "debug xpath"
     ly_cmd "load modmust" "XPATH"
 }}
 
 test debug_dep_sets {Check debug message DEPSETS} {
--setup $ly_setup -cleanup $ly_cleanup -constraints {[ly_cmd_exists "debug"]} -body {
+-setup $ly_setup -cleanup $ly_cleanup -constraints {[yanglint_debug]} -body {
     ly_cmd "verb debug"
     ly_cmd "debug dep-sets"
     ly_cmd "load modleaf" "DEPSETS"
 }}
 
 test debug_depsets_xpath {Check debug message DEPSETS and XPATH} {
--setup $ly_setup -cleanup $ly_cleanup -constraints {[ly_cmd_exists "debug"]} -body {
+-setup $ly_setup -cleanup $ly_cleanup -constraints {[yanglint_debug]} -body {
     ly_cmd "verb debug"
     ly_cmd "debug dep-sets xpath"
     ly_cmd "load modmust" "DEPSETS.*XPATH"
diff --git a/tools/lint/tests/interactive/ly.tcl b/tools/lint/tests/interactive/ly.tcl
index 612287a..df44bc3 100644
--- a/tools/lint/tests/interactive/ly.tcl
+++ b/tools/lint/tests/interactive/ly.tcl
@@ -174,26 +174,15 @@
     expect eof
 }
 
-# Check if yanglint supports the specified command.
-# Parameter cmd is a command to be found.
-# Return true if command is found otherwise false.
-proc ly_cmd_exists {cmd} {
-    global prompt
-    set rc true
-    spawn $::env(YANGLINT)
-    ly_skip_warnings
-
-    send -- "help\r"
-    expect -- "help\r\n"
-
-    set failure_pattern "\r\n${prompt}$"
-    expect {
-        -re "${cmd}.*\r\n${prompt}$" {}
-        -re $failure_pattern {
-            set rc false
-        }
+# Check if yanglint is configured as DEBUG.
+# Return 1 on success.
+proc yanglint_debug {} {
+    # Call non-interactive yanglint with --help.
+    set output [exec -- $::env(YANGLINT) "-h"]
+    # Find option --debug.
+    if { [regexp -- "--debug=GROUPS" $output] } {
+        return 1
+    } else {
+        return 0
     }
-
-    ly_exit
-    return $rc
 }