Hello! I'm seeing this as well (debdelta 0.56, Debian testing), and the changed proposed by TonyMi (see above) seems to fix it for me.
Patch attached. Thanks! Alex
--- /usr/bin/debdelta.orig 2017-01-01 23:58:49.000000000 +0100 +++ /usr/bin/debdelta 2017-01-20 14:03:11.408818733 +0100 @@ -4604,10 +4604,9 @@ return e, None, None, None else: #use urllib2 try: - if uri_p.scheme == 'http': - a=[copy(z) for z in uri_p] - a[2]=urllib2.quote(uri_p[2]) - url=urlunparse(a) + a=[copy(z) for z in uri_p] + a[2]=urllib2.quote(uri_p[2]) + url=urlunparse(a) req = urllib2.Request(url, headers=headers) r = urllib2.urlopen(req) #print r.info(),dir(r),r.code