Fix error class name raised by umount failed.

pym/cl_builder.py

@@ -220,7 +220,7 @@ class cl_builder(color_print):
             self.printMessageForTest(_("Unmounting %s")%(target[len(mp):]))
             umountProcess = process("umount",target)
             if umountProcess.failed():
-                raise AssembleError(_("Can not umount %s")%target)
+                raise BuilderError(_("Can not umount %s")%target)
             self.printByResult(True)
         distrPath = distr.convertToDirectory().getDirectory()
         self.cleanNeedlessKernelData(distrPath)