test: add some tracing to the svg validity test

It's a bit hard to figure out from the CI logs what failed because they
may be truncated. And for users not intimitely familiar with the test
suite it's not that simple either so let's put in a bunch of trace
stataments that should at least point to where things go wrong.

test/test-tablet-svg-validity.c

@@ -36,6 +36,9 @@
 #include <glib.h>
 #include "libwacom.h"
 
+#define trace(fmt, ...) \
+	fprintf(stderr, "%s: checking " fmt "\n", __func__,  __VA_ARGS__)
+
 static xmlNodePtr
 verify_has_sub (xmlNodePtr cur, char *sub)
 {
@@ -79,12 +82,13 @@ class_found (gchar **classes, gchar *value)
 static void
 verify_has_class (xmlNodePtr cur, const gchar *expected)
 {
-
 	xmlChar *prop;
 	gchar  **classes_present;
 	gchar  **classes_expected;
 	gchar  **ptr;
 
+	trace("%s", expected);
+
 	prop = xmlGetProp (cur, (xmlChar *) "class");
 	g_assert (prop != NULL);
 	g_assert (strlen((const char *) prop) > 0);
@@ -109,6 +113,8 @@ check_button (xmlNodePtr cur, const WacomDevice *device, char button, gchar *typ
 	xmlNodePtr        node;
 	WacomButtonFlags  flags;
 
+	trace("%c %s", button, type);
+
 	/* Check ID */
 	sub = g_strdup_printf ("%s%c", type, button);
 	node = verify_has_sub (cur, sub);
@@ -132,6 +138,8 @@ check_touchstrip (xmlNodePtr cur, gchar *id)
 	char             *class;
 	xmlNodePtr        node;
 
+	trace("%s", id);
+
 	node = verify_has_sub (cur, id);
 	g_assert (node != NULL);
 
@@ -234,6 +242,8 @@ check_touchring (xmlNodePtr cur, gchar *id)
 	char             *class;
 	xmlNodePtr        node;
 
+	trace("%s", id);
+
 	node = verify_has_sub (cur, id);
 	g_assert (node != NULL);