[libcalamaresui] Complain about missing config files

- When no config file is found, tell where it wasn't.

src/libcalamaresui/modulesystem/Module.cpp

@@ -169,7 +169,8 @@ moduleConfigurationCandidates( bool assumeBuildDir, const QString& moduleName, c
 void
 Module::loadConfigurationFile( const QString& configFileName ) //throws YAML::Exception
 {
-    foreach ( const QString& path, moduleConfigurationCandidates( Settings::instance()->debugMode(), m_name, configFileName ) )
+    QStringList configCandidates = moduleConfigurationCandidates( Settings::instance()->debugMode(), m_name, configFileName );
+    for ( const QString& path : configCandidates )
     {
         QFile configFile( path );
         if ( configFile.exists() && configFile.open( QFile::ReadOnly | QFile::Text ) )
@@ -198,6 +199,7 @@ Module::loadConfigurationFile( const QString& configFileName ) //throws YAML::Ex
             return;
         }
     }
+    cDebug() << "No config file found in" << Logger::DebugList( configCandidates );
 }