Import the "call" function from ffs into xapi.storage.common

This is useful for very simple storage backends.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>

python/xapi/storage/__init__.py

@@ -0,0 +1 @@
+#!/usr/bin/env python

python/xapi/storage/common.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python
+
+from xapi.storage import log
+import xapi
+import subprocess
+
+
+# [call dbg cmd_args] executes [cmd_args]
+# if [error] and exit code != expRc, log and throws a BackendError
+# if [simple], returns only stdout
+
+
+def call(dbg, cmd_args, error=True, simple=True, expRc=0):
+    log.debug("%s: Running cmd %s" % (dbg, cmd_args))
+    p = subprocess.Popen(
+        cmd_args,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        close_fds=True)
+    stdout, stderr = p.communicate()
+    if error and p.returncode != expRc:
+        log.error("%s: %s exitted with code %d: %s" %
+                  (dbg, " ".join(cmd_args), p.returncode, stderr))
+        raise xapi.InternalError("%s exitted with non-zero code %d: %s"
+                                 % (" ".join(cmd_args), p.returncode, stderr))
+    if simple:
+        return stdout
+    return stdout, stderr, p.returncode