csmock-snyk-plugin: no supported projects fix

Fix: https://issues.redhat.com/browse/OSH-329

If no supported project is detected using the snyk plugin, it no longer crashes but it does return 0

py/plugins/snyk.py

@@ -170,7 +170,11 @@ def scan_hook(results, mock, props):
             mock.exec_chroot_cmd("/bin/rm -fv %s" % auth_token_dst)
 
             # check exit code of snyk code itself
-            if ec not in [0, 1]:
+            if ec == 3:
+                 # If there are no supported project, we just return a successful scan without results
+                results.print_with_ts("snyk-code: no supported projects detected")
+                return 0
+            elif ec not in [0, 1]:
                 results.error("snyk code returned unexpected exit status: %d" % ec, ec=ec)
 
             # returning non-zero would prevent csmock from archiving SNYK_LOG