run-dev: fix typo sys.path -> sys.argv

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>
run-{check,tests}: global sanity check + prologue for tests

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>
run-{check,tests}: limit inferference with user's modules

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>