Include fewer paths in exception

It's sufficient to append them to the log.

Author: amcasey

src/services/services.ts

@@ -1158,7 +1158,7 @@ namespace ts {
         function getValidSourceFile(fileName: string): SourceFile {
             const sourceFile = program.getSourceFile(fileName);
             if (!sourceFile) {
-                throw new Error(`Could not find sourceFile: '${fileName}' in ${program && JSON.stringify(program.getSourceFiles().map(f => f.fileName))}.`);
+                throw new Error(`Could not find sourceFile: '${fileName}'.`);
             }
             return sourceFile;
         }