httppeer: eliminate decompressresponse() proxy

httppeer: eliminate decompressresponse() proxy

Now that the response instance itself is wrapped with error
handling, we no longer need this code. This code became dead
with the previous patch because the added code catches
HTTPException and re-raises as something else.

--- a/mercurial/httppeer.py	Fri Apr 14 00:33:56 2017 -0700
+++ b/mercurial/httppeer.py	Fri Apr 14 00:03:30 2017 -0700
@@ -31,30 +31,6 @@
 urlerr = util.urlerr
 urlreq = util.urlreq
 
-# FUTURE: consider refactoring this API to use generators. This will
-# require a compression engine API to emit generators.
-def decompressresponse(response, engine):
-    try:
-        reader = engine.decompressorreader(response)
-    except httplib.HTTPException:
-        raise IOError(None, _('connection ended unexpectedly'))
-
-    # We need to wrap reader.read() so HTTPException on subsequent
-    # reads is also converted.
-    # Ideally we'd use super() here. However, if ``reader`` isn't a new-style
-    # class, this can raise:
-    # TypeError: super() argument 1 must be type, not classobj
-    origread = reader.read
-    class readerproxy(reader.__class__):
-        def read(self, *args, **kwargs):
-            try:
-                return origread(*args, **kwargs)
-            except httplib.HTTPException:
-                raise IOError(None, _('connection ended unexpectedly'))
-
-    reader.__class__ = readerproxy
-    return reader
-
 def encodevalueinheaders(value, header, limit):
     """Encode a string value into multiple HTTP headers.
 
@@ -297,9 +273,11 @@
                 raise error.RepoError(_("'%s' sent a broken Content-Type "
                                         "header (%s)") % (safeurl, proto))
 
+            # TODO consider switching to a decompression reader that uses
+            # generators.
             if version_info == (0, 1):
                 if _compressible:
-                    return decompressresponse(resp, util.compengines['zlib'])
+                    return util.compengines['zlib'].decompressorreader(resp)
                 return resp
             elif version_info == (0, 2):
                 # application/mercurial-0.2 always identifies the compression
@@ -307,13 +285,13 @@
                 elen = struct.unpack('B', resp.read(1))[0]
                 ename = resp.read(elen)
                 engine = util.compengines.forwiretype(ename)
-                return decompressresponse(resp, engine)
+                return engine.decompressorreader(resp)
             else:
                 raise error.RepoError(_("'%s' uses newer protocol %s") %
                                       (safeurl, version))
 
         if _compressible:
-            return decompressresponse(resp, util.compengines['zlib'])
+            return util.compengines['zlib'].decompressorreader(resp)
 
         return resp