Use settings module for blacklisting

Signed-off-by: Hiroshi Miura <miurahr@linux.com>

aqt/helper.py

@@ -0,0 +1,42 @@
+import xml.etree.ElementTree as ElementTree
+
+import requests
+
+
+def altlink(url, priority=None, blacklist=None):
+    '''Download .meta4 metalink version4 xml file and parse it.'''
+
+    mirrors = {}
+    url = url
+    try:
+        m = requests.get(url + '.meta4')
+    except requests.exceptions.ConnectionError:
+        return
+    else:
+        mirror_xml = ElementTree.fromstring(m.text)
+        for f in mirror_xml.iter("{urn:ietf:params:xml:ns:metalink}file"):
+            for u in f.iter("{urn:ietf:params:xml:ns:metalink}url"):
+                pri = u.attrib['priority']
+                mirrors[pri] = u.text
+
+    if len(mirrors) == 0:
+        # no alternative
+        return url
+    if priority is None:
+        if blacklist is not None:
+            for ind in range(len(mirrors)):
+                mirror = mirrors[str(ind + 1)]
+                black = False
+                for b in blacklist:
+                    if mirror.startswith(b):
+                        black = True
+                        continue
+                if black:
+                    continue
+                return mirror
+        else:
+            for ind in range(len(mirrors)):
+                mirror = mirrors[str(ind + 1)]
+                return mirror
+    else:
+        return mirrors[str(priority)]