Add some attempts to mount partition with mount retcode 2816.

Some times (after change id) udev do not has time to re-create device in
/dev at the moment mounting for unpacking. The solution is some
attempts to mount this partition if mount has retcode 2816.

pym/cl_distr.py

@@ -565,8 +565,9 @@ class Distributive(object, SignalInterrupt):
         return None
 
 
-    def _mountToDirectory(self,file,directory,mountopts=""):
+    def _mountToDirectory(self,file,directory,mountopts="",count=2):
         """Mount squashfs to directory"""
+        NO_SUCH_DEVICE = 2816
         if isMount(directory):
             raise DistributiveError(_("Cann't mount to directory: %s\n")\
                                      %directory+ _("Directory already mounted"))
@@ -577,6 +578,12 @@ class Distributive(object, SignalInterrupt):
         if mountProcess.success():
             return True
         else:
+            # 2816 code return by mount if device is absent (update /dev by udev)
+            # try mount 3 times with interval 0.5 second
+            if mountProcess.returncode() == NO_SUCH_DEVICE and count:
+                sleep(0.5)
+                mountProcess.close()
+                return self._mountToDirectory(file,directory,mountopts,count-1)
             try:
                 self._removeDirectory(directory)
             except: