luis:build error messages do not work with imported files

[chrimc62]

Describe the bug

If you import an .lu file, error messages are with respect to the merged file--not specific to the imported files. This makes it very difficult to debug issues.

To Reproduce

Steps to reproduce the behavior:
1.Create an .lu file which imports another .lu file that has an error.
2. Run luis:build on the root .lu file

Expected behavior

Error messages refer to source file and line number.

[bug]

[feich-ms]

Will take a fix soon.

[vishwacsena]

We should probably include additional information on the file being parsed in the exception itself. I suspect this needs to be done in the core parser and not in luis:build. @feich-ms can you send me info on the fix you intended to make?

[feich-ms]

@vishwacsena, just did some investigations. The errors in imported files can be caught with line number correctly, however for import cases, the error message in lubuild is constructed as 'Invalid LU file ${root lu file path}: ${error message with line number from imported lg file}'. This is not reasonable. I will try to put lu object id in thrown err in parseLuFile function of luMerger.js file and consume this in lu build. Here is the PR #659