Fix-6911(pytest-bot): Added error from commands that are run
Fix-6911(pytest-bot): Added error from commands that are run

Earlier pytest-bot would only print out the exception in cases of
failure but did not provide context on failing command and error from
command. This patch adds the errors from the command to the exception
message.
`Command` provides abstraction over the command to run and helps
in collecting errors from the first failing command only.
With this, we don't need to check `returncode` from each command that
we run, we can run all the commands and will have access to the error
from the first command that failed. This pattern was taken from Go.
Please refer: https://blog.golang.org/errors-are-values

The-Compiler/pytest,nicoddemus/pytest,The-Compiler/pytest,markshao/pytest,pytest-dev/pytest,nicoddemus/pytest,RonnyPfannschmidt/pytest,Akasurde/pytest