[crmsh-4.6] Fix: sh: pass env to child process explicitly (bsc#1205925)

[nicholasyang2022]

A bug in python stardard library, python/cpython#100516, make
environment variables, COLUMNS and ROWS to be added at fork. These
environment variables may make some of the commands called by crmsh to
truncate its output even if those commands are not writing to the
terminal.

Passing argument env explicitly is a workaround for the python bug.

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 52.81%. Comparing base (24df92a) to head (1ceec36).
Report is 2 commits behind head on crmsh-4.6.

Files	Patch %	Lines
crmsh/term.py	33.33%	4 Missing ⚠️
crmsh/utils.py	33.33%	4 Missing ⚠️
crmsh/ui_node.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##           crmsh-4.6    #1356      +/-   ##
=============================================
- Coverage      52.82%   52.81%   -0.01%     
=============================================
  Files             79       79              
  Lines          24002    24011       +9     
=============================================
+ Hits           12678    12682       +4     
- Misses         11324    11329       +5     

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[liangxin1300]

LGTM, thanks!
Please backport to master

[nicholasyang2022]

Further experiment shows that the behavior of modifying environ COLUMNS and ROWS exists in libreadline, instead of the python wrapper.

[nicholasyang2022]

CPython backtrace: https://gist.github.com/nicholasyang2022/ce30ffc409ef3069f8b5628fa4b3d429

[nicholasyang2022]

The backtrace shows that COLUMNS is set when rl_initialize() is called from import readline. I had believed the environ is set at fork. However, this is not true. I use /proc/$pid/environ to determine whether COLUMNS is set. This is also unreliable as it is not updated instantly when setenv(3) is called.

From proc_pid_environ(5):

this file contains the initial environment that was set when the
currently executing program was started via execve(2)

If, after an execve(2), the process modifies its environment
(e.g., by calling functions such as putenv(3) or modifying the
environ(7) variable directly), this file will not reflect those
changes.