The "new gui wizard" uses the deprecated "MONITOR" key

[cpascual]

When TaurusGUI loads its configuration, it supports (for backwards compatibility) a deprecated MONITOR key in the configuration. When present, a deprecated taurus.qt.qtgui.qwt5.TaurusMonitorTiny class is used (Taurus assumes that this key is only present in old configurations, which are associated with availability of old plot implementations).

When one such configuration is loaded in a system using python3 or Qt5, the TaurusMonitorTiny is not available (because the old Qwt5 module is not available), and a KeyError: 'TaurusMonitorTiny' exception is raised on load, potentially messing with the load of other configurations.

This was not considered a critical issue because the "MONITOR" key has been deprecated for a very long time in favor of the AppletDescriptions mechanism. But it turns out that the AppSettingsWizard (used with taurus newgui) has a "monitor" page that accepts a list of attributes and sets it as the value of the MONITOR key in the configuration xml.

In order to fix, I propose:

• to handle the exception in TaurusGui._loadCustomApplets to make it more robust
• refactor the AppSettingsWizard to stop creating "MONITOR" keys
• (optional) implement a replacement for TaurusMonitorTiny in taurus_pyqtgraph (in order to improve backwards compatibility)