Add configuration check for specified templates

part of #683

core/lib/patternlab.js

@@ -122,10 +122,16 @@ function checkConfiguration(patternlab) {
   if (!patternlab.config.outputFileSuffixes) {
     plutils.warning('Configuration Object "outputFileSuffixes" not found, and defaulted to the following:');
     console.log(outputFileSuffixes);
-    plutils.warning('Since Pattern Lab Core 2.3.0 this configuration option is required. Suggest you add it to your patternlab-config.json file.');
+    plutils.warning('Since Pattern Lab Node Core 2.3.0 this configuration option is required. Suggest you add it to your patternlab-config.json file.');
     console.log();
   }
   patternlab.config.outputFileSuffixes = _.extend(outputFileSuffixes, patternlab.config.outputFileSuffixes);
+
+  if (typeof patternlab.config.paths.source.patternlabFiles === 'string') {
+    plutils.warning(`Configuration key [paths.source.patternlabFiles] inside patternlab-config.json was found as the string '${patternlab.config.paths.source.patternlabFiles}'`);
+    plutils.warning('Since Pattern Lab Node Core 3.0.0 this key is an object. Suggest you update this key following this issue: https://github.com/pattern-lab/patternlab-node/issues/683.');
+  }
+
 }
 
 /**