issue1002-Setting nx, ny, nz to non-positive integer should generate an error

[sridhar-mani]

Tried to correct the issue No.1002.Included validation checks for the inputs.

Setting nx, ny, nz to non-positive integer should generate an error #1002

[guyer]

Thank you very much for the contribution. As you can see, this PR currently generates a lot of test failures. Most seem to be because of where you do the check. For non-uniform grids, the default value for nx, ny, and nz is None, which fails your checks.

• I think the correct place to make this check is in _NonuniformNumPts.calcNs() and _UniformNumPts.calcNs().
• I don't see any need for a try ... except ... block. The check should just fail.
  • If you really don't want the failure, then it should raise a Warning, but definitely not print out an error message.
• Please remove the addition of .vscode/settings.json. It doesn't seem to have anything to do with this PR. If you'd like to separately propose VSCode settings, please make a separate PR and explain your rationale (I don't use VSCode, so I don't know what makes sense as a project setting vs. a personal setting).