Load Wizard in XML Mode forcing Accept header to application/xml

[sgrellet]

Environment

• Plugin version: 1.3.1
• QGIS version: 3.16.2-Hannover Hannover, f1660f9da5
• Operating System: Windows 10
• Python version: 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)]

Description

• when accessing URLs(URIs) in 'XML Mode' via the 'Load Wizard', the Accept header is set to application/xml instead of either nothing (to allow passing a GET param like f=application%2Fgml%2Bxml) or directly application/gml+xml
• this may cause issues when content negociation happens with the server.

To Reproduce

Steps to reproduce the behavior:

1. Load Wizard > File/URL : http://iddata.eaufrance.fr/id/HydroStation/A021005050
2. Loading options > 'Load in XML mode'
3. Next and Finish

-> Python error
Stack trace below

Expected behavior

• The GML content is properly fetched from the URL/I and added to the QGIS Layer

---

Additional context

• QGIS 'Network Logger' (F12) shows an Accept header set to application/xml
• querying that URI in a application such as PostMan with Accept header set to application/xml leads to the following error => {"code": "NoApplicableCode", "description": "Could not find acceptable representation"}
• querying that URI in a application such as PostMan with Accept header set to application/gml+xml allows to fetch the GML representation

Logs

AttributeError: 'NoneType' object has no attribute 'close' 
Traceback (most recent call last):
  File "C:/Users/grellets/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\gml_application_schema_toolbox\core\load_gml_as_xml.py", line 386, in load_complex_gml
    src = ComplexFeatureSource(xml_src, attributes, geometry_mapping, logger)
  File "C:/Users/grellets/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\gml_application_schema_toolbox\core\load_gml_as_xml.py", line 249, in __init__
    doc, _ = xml_parse(xml)
  File "C:/Users/grellets/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\gml_application_schema_toolbox\core\xml_utils.py", line 118, in xml_parse
    for event, elem in ET.iterparse(xml_file, ["start-ns", "start", "end"]):
  File "C:\PROGRA~1\QGIS3~1.16\apps\Python37\lib\xml\etree\ElementTree.py", line 1243, in iterparse
    source = open(source, "rb")
TypeError: expected str, bytes or os.PathLike object, not NoneType

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:/Users/grellets/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\gml_application_schema_toolbox\gui\load_wizard_xml.py", line 79, in validatePage
    swap_xy=self.swapXYCheck.isChecked(),
  File "C:/Users/grellets/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\gml_application_schema_toolbox\core\load_gml_as_xml.py", line 71, in load_as_xml_layer
    xml_uri, is_remote, attributes, geometry_mapping, logger, swap_xy
  File "C:/Users/grellets/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\gml_application_schema_toolbox\core\load_gml_as_xml.py", line 468, in load_complex_gml
    xml_src.close()
AttributeError: 'NoneType' object has no attribute 'close'