Use https by default with CAA but not for custom servers

This adds a new "global" `https` boolean variable. This variable will be
True by default, but if `set_hostname()` gets called it will default to
False. This should allow both using coverartarchive.org over HTTPS by
default, but anyone that have a script setting a custom server (that may
not support HTTPS) will continue to work as well.

Related to alastair#197

Signed-off-by: Frederik “Freso” S. Olesen <freso.dk@gmail.com>

musicbrainzngs/caa.py

@@ -16,13 +16,16 @@
 from musicbrainzngs.util import _unicode
 
 hostname = "coverartarchive.org"
+https = True
 
 
-def set_caa_hostname(new_hostname):
+def set_caa_hostname(new_hostname, use_https=False):
     """Set the base hostname for Cover Art Archive requests.
     Defaults to 'coverartarchive.org'."""
     global hostname
+    global https
     hostname = new_hostname
+    https = use_https
 
 
 def _caa_request(mbid, imageid=None, size=None, entitytype="release"):
@@ -46,7 +49,7 @@ def _caa_request(mbid, imageid=None, size=None, entitytype="release"):
     elif imageid:
         path.append(imageid)
     url = compat.urlunparse((
-        'http',
+        'https' if https else 'http',
         hostname,
         '/%s' % '/'.join(path),
         '',