Use Python 3 compatible syntax for exceptions

Fix non-usable toolbar on wxPython with GTK3+ in PLCOpenEditor

this problem is related to 'Fix non-usable toolbar on wxPython with
GTK3+' (5927710b). This problem does not happen in Beremiz because
additional necessary self.AUIManager.Update() is called
BeremizIDE. Therefore minimal change in the mentioned commit was
enough for Beremiz, but is not enough for PLCOpenEditor.

Avoid usage of localized strings before initialization during import in many modules

This happens if import is done before i18n setup
(InstallLocalRessources()).
This affects PLCOpenEditor mostly. Beremiz IDE is free from this issue, but moving
initialization from import should make modules more robust.
Otherwise execution result depends on where and when import was done
and this is not a good thing.

Some modules (ConfigTreeNode, features, CodeFileEditor related
classes) still have this, but they are used only in Beremiz.
Most problems result in non-working internatialization.
In some cases (VariablePanel) there is backtrace, because localized
key is not found in non-localized dictionary.

Remove executable bit from source files where it's not needed.