Add error message for Xarray pickling.

[DanielAdriaansen]

Describe the Problem

Here:

MET/met/src/libcode/vx_data2d_python/python_dataplane.cc

Line 437 in 2c9ae44

exit ( 1 );

we exit(1) without printing an error message to the user! We should issue a bug fix to print an error message.

For met-10.0, we should implement support for Xarray Python embedding with pickling. That work is described in #1534 .

Expected Behavior

I expect a warning message instead of MET silently exiting and producing no output.

Environment

Describe your runtime environment:
*1. Machine: kiowa

To Reproduce

To force pickling, set the MET_PYTHON_EXE environment variable. This can be set to any version of Python I think, which just forces invocation of the pickling logic in MET which is necessary to reproduce the error.
export MET_PYTHON_EXE=/path/to/python

Call a test script I wrote for Xarray Python embedding
/usr/local/met-9.1/bin/plot_data_plane PYTHON_XARRAY testXR.ps 'name="/home/dadriaan/projects/remote/read_ascii_xarray.py /home/dadriaan/git/met/met/data/python/fcst.txt FCST";' -title "Testing" -v 10

Relevant Deadlines

NONE

Funding Source

Define the source of funding and account keys here or state NONE.

Define the Metadata

Assignee

• Select engineer(s) or no engineer required
• Select scientist(s) or no scientist required

Labels

• Select component(s)
• Select priority
• Select requestor(s)

Projects and Milestone

• Review projects and select relevant Repository and Organization ones
• Select milestone

Define Related Issue(s)

Consider the impact to the other METplus components.

• METplus, MET, METdatadb, METviewer, METexpress, METcalcpy, METplotpy

Bugfix Checklist

See the METplus Workflow for details.

• Complete the issue definition above.
• Fork this repository or create a branch of master_<Version>.
  Branch name: bugfix_<Issue Number>_master_<Version>_<Description>
• Fix the bug and test your changes.
• Add/update unit tests.
• Add/update documentation.
• Push local changes to GitHub.
• Submit a pull request to merge into master_<Version> and link the pull request to this issue.
  Pull request: bugfix <Issue Number> master_<Version> <Description>
• Iterate until the reviewer(s) accept and merge your changes.
• Delete your fork or branch.
• Complete the steps above to fix the bug on the develop branch and link the pull request to this issue.
  Branch name: bugfix_<Issue Number>_develop_<Description>
  Pull request: bugfix <Issue Number> develop <Description>
• Close this issue.

[JohnHalleyGotway]

Committed minor tweaks to log messages in python_dataplane.cc directly to the main_v9.1 and develop branches. Note that this does not follow best practices of submitting PR's for code changes.