Fix python importing-error handling

[ichizok]

Problem

When importing python module, there is the case that the error occurred from module is incorrect.
(both +python and +python3)

Repro steps

/path/to/vim is Vim git repository.
The following step uses failing_import.py module in vim/src/testdir/pythonx.

$ cat /path/to/vim/src/testdir/pythonx/failing_import.py
raise ImportError

start Vim:

vim --clean

:set rtp+=/path/to/vim/src/testdir
:py import failing_import

then get ImportError:

Expected: ImportError() (empty message)
Actual: ImportError('No module named failing_import) (below)

Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: No module named failing_import

ImportError reports "No module named" though failing_import module exists.
That is, ImportError emitted from module inside is not propagated correctly.

Also python3.

Cause

vim.find_module does both finding and loading all intermediate packages and module, so ImportError in loading is treated as the error in finding module.

Solution

• Do loading final module (does not include . in its name) in vim.load_module

[ichizok]

Sorry, I made a mistake in repro steps:

:set rtp+=/path/to/vim/src/testdir/pythonx

correct: :set rtp+=/path/to/vim/src/testdir (drop /pythonx)

[codecov-io]

Codecov Report

Merging #3162 into master will increase coverage by <.01%.
The diff coverage is 60.52%.

@@            Coverage Diff             @@
##           master    #3162      +/-   ##
==========================================
+ Coverage   76.55%   76.55%   +<.01%     
==========================================
  Files          93       93              
  Lines      136839   136857      +18     
==========================================
+ Hits       104752   104769      +17     
- Misses      32087    32088       +1

Impacted Files	Coverage Δ
src/if_py_both.h	76.31% <60.52%> (-0.26%)	⬇️
src/os_unix.c	57.42% <0%> (-0.14%)	⬇️
src/window.c	81.9% <0%> (+0.03%)	⬆️
src/channel.c	83.15% <0%> (+0.03%)	⬆️
src/getchar.c	75.21% <0%> (+0.04%)	⬆️
src/normal.c	74.42% <0%> (+0.07%)	⬆️
src/ex_cmds2.c	82.72% <0%> (+0.09%)	⬆️
src/gui.c	49.58% <0%> (+0.2%)	⬆️
src/version.c	82.95% <0%> (+0.89%)	⬆️

---

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[brammool]

Can you update this pull request for the latest changes?

[ichizok]

Thank you, I updated this.

[eirnym]

The coverage dropped probably because of whitespace changes.

[brammool]

The coverage dropped probably because of whitespace changes.

So is this ready to be included now?

…

-- Seen on the back of a biker's vest: If you can read this, my wife fell off. /// Bram Moolenaar -- Bram@Moolenaar.net -- http://www.Moolenaar.net \\\ /// sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\ \\\ an exciting new programming language -- http://www.Zimbu.org /// \\\ help me help AIDS victims -- http://ICCF-Holland.org ///

[eirnym]

LGTM

[ichizok]

@brammool This patch is ready to be merged.