factor out common code into a function...

casimport/__init__.py

@@ -105,6 +105,13 @@ def tempattrset(obj, key, value):
 		else:
 			delattr(obj, key)
 
+def urlfetch(url):
+	with urllib.request.urlopen(url) as req:
+		if req.status // 100 != 2:
+			raise RuntimeError('bad fetch')
+
+		return req.read()
+
 class HTTPSCAS(object):
 	def fetch_data(self, url):
 		if url.scheme != 'https':
@@ -112,11 +119,7 @@ class HTTPSCAS(object):
 			    repr(url.scheme))
 
 		url = urllib.parse.urlunparse(url)
-		with urllib.request.urlopen(url) as req:
-			if req.status // 100 != 2:
-				raise RuntimeError('bad fetch')
-
-			return req.read()
+		return urlfetch(url)
 
 class IPFSCAS(object):
 	gwhost = 'gateway.ipfs.io'
@@ -132,12 +135,7 @@ class IPFSCAS(object):
 			    repr(url.scheme))
 
 		gwurl = self.make_url(url)
-
-		with urllib.request.urlopen(gwurl) as req:
-			if req.status // 100 != 2:
-				raise RuntimeError('bad fetch')
-
-			return req.read()
+		return urlfetch(gwurl)
 
 class FileDirCAS(object):
 	'''A file loader for CAS that operates on a directory.  It looks