Proper fix for error 'object has no attribute 'getSlave' in EtherCAT extension

traceback:
File "/home/developer/WorkData/PLC/beremiz/beremiz/IDEFrame.py", line 1433, in OnPouSelectedChanged
window.RefreshView()
File "/home/developer/WorkData/PLC/beremiz/beremiz/etherlab/ConfigEditor.py", line 837, in RefreshView
self.RefreshProcessVariables()
File "/home/developer/WorkData/PLC/beremiz/beremiz/etherlab/ConfigEditor.py", line 886, in RefreshProcessVariables
slaves = self.Controler.GetSlaves(**self.CurrentNodesFilter)
File "/home/developer/WorkData/PLC/beremiz/beremiz/etherlab/EthercatMaster.py", line 341, in GetSlaves
for slave in self.Config.getConfig().getSlave():
<type 'exceptions.AttributeError'>:_'lxml.etree._Element'_object_has_no_attribute_'getSlave'

Steps to reproduce problem:

- Add new EtherCAT master
- Add new EthercatNode to the master
- double click on


Revert commit "Dirty fix for error '_object_has_no_attribute_'getSlave' in EtherCAT extension"
[a3ac46366b86a0b237dac93be6b2281ac70b98a8].

The problem was that XML elements (proxy object) in some cases were created using custom XML
classes constructors and lxml.etree.Element() call and live python
patching. This causes that lxml backend doesn't know that custom python class
should be used for these XML elements.
Proxy object can be move/deleted and recreated by lxml
backend at any point in time or this can be done in python by copy/deepcopy operations.
If this happens, then newly created
proxy elements are using default class lxml.etree._Element. And all
custom functionality is lost.

All created XML elements should be always created through corresponding
parser and class lookup callback done by lxml backend.
It's described in more details in lxml documentation:
https://lxml.de/element_classes.html

     1

# SOME DESCRIPTIVE TITLE.

     2

# Copyright (C) is 21st century inquisition

     3

# This file is distributed under the same license as the Beremiz package.

     4

# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.

     5

#

     6

msgid ""

     7

msgstr ""

     8

"Project-Id-Version: Beremiz 1.1\n"

     9

"Report-Msgid-Bugs-To: \n"

    10

"POT-Creation-Date: 2012-09-08 00:41\n"

    11

"PO-Revision-Date: 2012-09-07 10:53+0100\n"

    12

"Last-Translator: \n"

    13

"Language-Team: \n"

    14

"Language: \n"

    15

"MIME-Version: 1.0\n"

    16

"Content-Type: text/plain; charset=UTF-8\n"

    17

"Content-Transfer-Encoding: 8bit\n"

    18

"X-Poedit-Language: French\n"

    19

"X-Poedit-Country: FRANCE\n"

    20

"X-Poedit-SourceCharset: utf-8\n"

    21

    22

# c9c5ea5d04e64cb6a54fcda391cb4929

    23

#: ../../manual/install.rst:2

    24

msgid "Beremiz installation"

    25

msgstr "Installation de Beremiz"

    26

    27

# 3f78e50eff364a0abbfcb8cf9a0a68da

    28

#: ../../manual/install.rst:5

    29

msgid "Windows"

    30

msgstr "WIndows"

    31

    32

# 963db7a095b246d68c4a51163b441952

    33

#: ../../manual/install.rst:6

    34

msgid "Download installer, install."

    35

msgstr "Téléchergez l'installeur, exécutez le."

    36

    37

# 87380693201647979e3c0d0527205575

    38

#: ../../manual/install.rst:9

    39

msgid "Linux"

    40

msgstr "Linux"

    41

    42

# 0c4d6e88a20248b9bc3b167cf120c318

    43

#: ../../manual/install.rst:10

    44

msgid "Pre-requisites::"

    45

msgstr "Pre-requis::"

    46

    47

# ced14d340a194a2b9f53b8e6c34d6804

    48

#: ../../manual/install.rst:16

    49

msgid "Prepare::"

    50

msgstr "Préparation::"

    51

    52

# f555cb10ef0d42d6bbbe2f85f0763057

    53

#: ../../manual/install.rst:21

    54

msgid "Get Source Code::"

    55

msgstr "Obtenir le code source::"

    56

    57

# 1d5926626d3b49d891529b9fc687fec3

    58

#: ../../manual/install.rst:29

    59

msgid "Build MatIEC compiler::"

    60

msgstr "Compiler le compilateur MatIEC::"

    61

    62

# 166772d03f6f4d67abb4ed849fc3f6d8

    63

#: ../../manual/install.rst:35

    64

msgid "Build CanFestival (optional)::"

    65

msgstr "Compiler CanFestival::"

    66

    67

# 39a65c2b7ca747438a15d31bd4a40a4f

    68

#: ../../manual/install.rst:47

    69

msgid "Launch Beremiz::"

    70

msgstr "Lancer Beremiz::"