remove support for XML app metadata, its broken

JSON and YAML are very closely related, so supporting both of them is
basically almost no extra work.  Both are also closely related to how
Python works with dicts and pickles. XML is a very different beast, and its
not popular for this kind of thing anyway, so just purge it.

fdroidserver/metadata.py

@@ -35,9 +35,6 @@ except ImportError:
     from yaml import Loader
     YamlLoader = Loader
 
-# use the C implementation when available
-import xml.etree.cElementTree as ElementTree
-
 import fdroidserver.common
 
 srclibs = None
@@ -804,10 +801,8 @@ def read_metadata(xref=True, check_vcs=[]):
 
     for metadatapath in sorted(glob.glob(os.path.join('metadata', '*.txt'))
                                + glob.glob(os.path.join('metadata', '*.json'))
-                               + glob.glob(os.path.join('metadata', '*.xml'))
                                + glob.glob(os.path.join('metadata', '*.yml'))
                                + glob.glob('.fdroid.json')
-                               + glob.glob('.fdroid.xml')
                                + glob.glob('.fdroid.yml')):
         packageName, _ = fdroidserver.common.get_extension(os.path.basename(metadatapath))
         if packageName in apps:
@@ -987,8 +982,6 @@ def parse_metadata(metadatapath, check_vcs=False):
             parse_txt_metadata(mf, app)
         elif ext == 'json':
             parse_json_metadata(mf, app)
-        elif ext == 'xml':
-            parse_xml_metadata(mf, app)
         elif ext == 'yml':
             parse_yaml_metadata(mf, app)
         else:
@@ -1032,38 +1025,6 @@ def parse_json_metadata(mf, app):
     return app
 
 
-def parse_xml_metadata(mf, app):
-
-    tree = ElementTree.ElementTree(file=mf)
-    root = tree.getroot()
-
-    if root.tag != 'resources':
-        warn_or_exception('resources file does not have root element <resources/>')
-
-    for child in root:
-        if child.tag != 'builds':
-            # builds does not have name="" attrib
-            name = child.attrib['name']
-
-        if child.tag == 'string':
-            app.set_field(name, child.text)
-        elif child.tag == 'string-array':
-            for item in child:
-                app.append_field(name, item.text)
-        elif child.tag == 'builds':
-            for b in child:
-                build = Build()
-                for key in b:
-                    build.set_flag(key.tag, key.text)
-                app.builds.append(build)
-
-    # TODO handle this using <xsd:element type="xsd:boolean> in a schema
-    if not isinstance(app.RequiresRoot, bool):
-        app.RequiresRoot = app.RequiresRoot == 'true'
-
-    return app
-
-
 def parse_yaml_metadata(mf, app):
 
     yamlinfo = yaml.load(mf, Loader=YamlLoader)