RunCmd: log command line for missing cmd case

In case of missing programs, currently utils.RunCmd doesn't show any
information to help debugging, only 'No such file or directory'. This
patch adds error handling for the ENOENT case such that at least we have
this information in the node daemon logs.
Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

lib/utils.py

@@ -151,11 +151,18 @@ def RunCmd(cmd, env=None, output=None, cwd='/'):
   if env is not None:
     cmd_env.update(env)
 
-  if output is None:
-    out, err, status = _RunCmdPipe(cmd, cmd_env, shell, cwd)
-  else:
-    status = _RunCmdFile(cmd, cmd_env, shell, output, cwd)
-    out = err = ""
+  try:
+    if output is None:
+      out, err, status = _RunCmdPipe(cmd, cmd_env, shell, cwd)
+    else:
+      status = _RunCmdFile(cmd, cmd_env, shell, output, cwd)
+      out = err = ""
+  except OSError, err:
+    if err.errno == errno.ENOENT:
+      raise errors.OpExecError("Can't execute '%s': not found (%s)" %
+                               (strcmd, err))
+    else:
+      raise
 
   if status >= 0:
     exitcode = status