COMPMID-417 Allow the tests to run even when assets are not present

Change-Id: Ief165b1d583a70cbe35aae93f05ddfe962196323
Reviewed-on: http://mpd-gerrit.cambridge.arm.com/89503
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Tested-by: Kaizen <jeremy.johnson+kaizengerrit@arm.com>
diff --git a/tests/framework/Exceptions.h b/tests/framework/Exceptions.h
index edb0ed9..f35c350 100644
--- a/tests/framework/Exceptions.h
+++ b/tests/framework/Exceptions.h
@@ -63,6 +63,17 @@
 ::std::ostream &operator<<(::std::ostream &stream, LogLevel level);
 std::string to_string(LogLevel level);
 
+/** Error class for when some external assets are missing */
+class FileNotFound : public std::runtime_error
+{
+public:
+    /** Construct error with message
+     *
+     * @param[in] msg Error message
+     */
+    FileNotFound(const std::string &msg);
+};
+
 /** Error class for failures during test execution. */
 class TestError : public std::runtime_error
 {