bdd: move external process execution in separate func

test/bdd/steps/utils.py

@@ -0,0 +1,22 @@
+"""
+Various smaller helps for step execution.
+"""
+import logging
+import subprocess
+
+LOG = logging.getLogger(__name__)
+
+def run_script(cmd, **kwargs):
+    """ Run the given command, check that it is successful and output
+        when necessary.
+    """
+    proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                            **kwargs)
+    (outp, outerr) = proc.communicate()
+    outp = outp.decode('utf-8')
+    outerr = outerr.decode('utf-8').replace('\\n', '\n')
+    LOG.debug("Run command: %s\n%s\n%s", cmd, outp, outerr)
+
+    assert proc.returncode == 0, "Script '{}' failed:\n{}\n{}\n".format(cmd[0], outp, outerr)
+
+    return outp, outerr