Complete support for Python Xarray embedding.

[JohnHalleyGotway]

Describe the Problem

I am splitting issue MET #1472 down into 2 pieces: 1 bugfix (#1472) and 1 enhancement (this issue). By the time we work on this issue, #1472 should have already been resolved.

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, and then implement the support for this section (Xarray Python embedding with pickling) for v10.0.

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

2791541

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[DanielAdriaansen]

@davidfillmore while doing some other work, I prototyped a "read_xarray_python.py" script based on the "read_numpy_python.py" script already in MET. You can view that script on kiowa:/home/dadriaan/projects/remote/read_xarray_python.py. There's also some information in kiowa:/home/dadriaan/projects/remote/remote_demo.py near the bottom where I conform the attributes of the Xarray DataArray object to the MET standards which may be useful and is related to #1470.

[dwfncar]

write_pickle_dataplane.py fails on system module imort
import importlib.util
System path issue?

[dwfncar]

write_pickle_dataplane is run by the user's python,
designated by MET_PYTHON_EXE.
This must be python 3 and have the importlib module available.

[dwfncar]

Added read_ascii_xarray to met/scripts/python.
This script currently fails within write_pickle_dataplane with module 'read_ascii_xarray' has no attribute 'atttrs'.