Description:
 Can not start TUI HE deployment process because of UI AttributeError.

An error appeared in the UI: AttributeError("'TransactionProgressDialog' object has no attribute 'event'",)
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or enter 's' to drop to shell


# rpm -q ovirt-node ovirt-hosted-engine-setup
ovirt-node-3.3.0-0.10.20150928gite7ee3f1.el7ev.noarch
ovirt-hosted-engine-setup-1.3.0-1.el7ev.noarch

# cat /etc/redhat-release 
Red Hat Enterprise Virtualization Hypervisor release 7.2 (20150928.0.el7ev)

Test Steps:
1. Installed RHEVH 7.2 (20150928.0.el7ev) for rhev 3.6.0 successful.
2. Setup Network yet
3. Deploy HE on RHEV-H TUI.
4. Enable "PXE Boot Engine VM"
5. Click on "Deploy"

Actual Result:
Can not start HE deployment process, break on UI AttributeError, then have to be back to shell.

Expected Result:
Can start HE deployment process without such error.

# ovirt-node.log
<snip>
2015-09-30 02:48:05,232      ERROR An error appeared in the UI: AttributeError("'TransactionProgressDialog' object has no attribute 'event'",)
2015-09-30 02:48:05,232       INFO Exception:
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/ovirt/node/app.py", line 304, in run
    self.ui.run()
  File "/usr/lib/python2.7/site-packages/ovirt/node/ui/urwid_builder.py", line 441, in run
    self.__loop.run()
  File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line 271, in run
    self.screen.run_wrapper(self._run)
  File "/usr/lib64/python2.7/site-packages/urwid/raw_display.py", line 241, in run_wrapper
    return fn()
  File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line 336, in _run
    self.event_loop.run()
  File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line 707, in run
    self._loop()
  File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line 786, in _loop
    self._watch_files[fd]()
  File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line 387, in _update
    self.process_input(keys)
  File "/usr/lib64/python2.7/site-packages/urwid/main_loop.py", line 487, in process_input
    k = self._topmost_widget.keypress(self.screen_size, k)
  File "/usr/lib64/python2.7/site-packages/urwid/container.py", line 566, in keypress
    *self.calculate_padding_filler(size, True)), key)
  File "/usr/lib64/python2.7/site-packages/urwid/container.py", line 1559, in keypress
    key = self.focus.keypress(tsize, key)
  File "/usr/lib64/python2.7/site-packages/urwid/container.py", line 2240, in keypress
    key = w.keypress((mc,) + size[1:], key)
  File "/usr/lib64/python2.7/site-packages/urwid/container.py", line 1559, in keypress
    key = self.focus.keypress(tsize, key)
  File "/usr/lib64/python2.7/site-packages/urwid/container.py", line 1559, in keypress
    key = self.focus.keypress(tsize, key)
  File "/usr/lib64/python2.7/site-packages/urwid/decoration.py", line 618, in keypress
    return self._original_widget.keypress(maxvals, key)
  File "/usr/lib64/python2.7/site-packages/urwid/container.py", line 1102, in keypress
    return self.body.keypress( (maxcol, remaining), key )
  File "/usr/lib/python2.7/site-packages/ovirt/node/ui/widgets.py", line 759, in keypress
    return super(TabablePile, self).keypress(size, key)
  File "/usr/lib64/python2.7/site-packages/urwid/container.py", line 1559, in keypress
    key = self.focus.keypress(tsize, key)
  File "/usr/lib64/python2.7/site-packages/urwid/decoration.py", line 833, in keypress
    return self._original_widget.keypress((maxcol,), key)
  File "/usr/lib64/python2.7/site-packages/urwid/container.py", line 2240, in keypress
    key = w.keypress((mc,) + size[1:], key)
  File "/usr/lib64/python2.7/site-packages/urwid/container.py", line 1559, in keypress
    key = self.focus.keypress(tsize, key)
  File "/usr/lib64/python2.7/site-packages/urwid/decoration.py", line 618, in keypress
    return self._original_widget.keypress(maxvals, key)
  File "/usr/lib64/python2.7/site-packages/urwid/wimp.py", line 534, in keypress
    self._emit('click')
  File "/usr/lib64/python2.7/site-packages/urwid/widget.py", line 463, in _emit
    signals.emit_signal(self, name, self, *args)
  File "/usr/lib64/python2.7/site-packages/urwid/signals.py", line 120, in emit
    result |= bool(callback(*args_copy))
  File "/usr/lib/python2.7/site-packages/ovirt/node/ui/widgets.py", line 542, in on_click_cb
    urwid.emit_signal(self, 'click', self)
  File "/usr/lib64/python2.7/site-packages/urwid/signals.py", line 120, in emit
    result |= bool(callback(*args_copy))
  File "/usr/lib/python2.7/site-packages/ovirt/node/ui/urwid_builder.py", line 111, in on_widget_click_cb
    ui_button.on_activate(change)
  File "/usr/lib/python2.7/site-packages/ovirt/node/base.py", line 103, in __call__
    self.emit(userdata)
  File "/usr/lib/python2.7/site-packages/ovirt/node/base.py", line 85, in emit
    if cb(self.target, userdata) is False:
  File "/usr/lib/python2.7/site-packages/ovirt/node/ui/__init__.py", line 201, in __call__
    r = self.callback(userdata)
  File "/usr/lib/python2.7/site-packages/ovirt/node/app.py", line 176, in call_on_ui_save
    self.current_plugin()._on_ui_save()
  File "/usr/lib/python2.7/site-packages/ovirt/node/plugins.py", line 406, in _on_ui_save
    successfull_merge = self.on_merge(effective_changes)
  File "/usr/lib/python2.7/site-packages/ovirt/node/setup/hostedengine/hosted_engine_page.py", line 267, in on_merge
    args=(progress_dialog.event,))
AttributeError: 'TransactionProgressDialog' object has no attribute 'event'
</snip>