If the flake8 executable is not found, the static test script reports
the tool as missing. It may happen that the flake8 module is installed,
but the console entry point is not.
In the flake8 shell script, flake is invoked via `python -m`. The result
is a confusing error message where static-test reports the tools as missing,
yet the flake8 tests are run.
This patch makes the toolchain version script use the same command as the
flake8 script.
Detect command line tool versions without using "command".
Command may be a builting in some shells, leading to unportability.
The new version uses the status code to correctly detect a non-existent
command. This allows it to differentiate between error in the tool and
not-found errors.
It also works with compound commands, for example `python -m callable_module".
Currently version information of commands and tools is only parsed
from STDOUT, however some tools like openocd print version info
to STDERR only. This commits adds parsing of STDERR for version
infos if STDOUT does not contain such info.
