[feat] Print error information when a modules system operation fails

[omlins]

Closes #467

[vkarak]

I think we should add another layer between the _exec_load_command() and the actual implementation of the backends. The backends should then throw a SpawnedProcessError, which will contain all the information of the failing command, i.e., command arguments, stdout, stderr, exit code. We should do sth like the following:

def exec_module_command(self, *args, msg=None):
    try:
        self._exec_module_command(self, *args)
    except SpawnedProcessError as e:
        raise EnvironError(msg) from e

The advantage of this is that when we print the top-level exception, the information of the exceptions that caused the problem are also printed. And in a uniform way (you don't have to deal with where to put the :).

[vkarak]

Following our discussion offline, the correct interface should be sth like the following:

    def _run_module_command(self, *args, msg=None):
        command = [self._command, *args]
        try:
            completed = os_ext.run_command(' '.join(command), check=True)
        except SpawnedProcessError as e:
            raise EnvironError(msg) from e

        # Check for ERROR inside the stderr as of now in _exec_module_command()
        if error:
            raise EnvironError(msg) from SpawnedProcessError(completed.command, completed.stdout, ...)

        return completed


    def _exec_module_command(self, *args, msg=None):
        completed = self._run_module_command(*args, msg)
        exec(completed.stdout)

[vkarak]

My comments are mostly related to coding style issues.

[vkarak]

@jenkins-cscs retry dom kesch

[omlins]

@jenkins-cscs retry dom kesch daint