py3: stop subscripting socket.error

In 3.3 and later, this is now an alias for OSError.  I hacked up the server code
enough that I was able to trigger the exception handler in server.py from
test-http-bundle1.t.  Other instances of this either subscript through the
`args` member, or reference the errno or strerror attributes.

Note that on Windows, the errno value seems to reflect the Winsock error, so the
various tests for EPIPE seem like they would always fail.  But that seems to be
the case in py2 as well.

mercurial/hgweb/server.py

@@ -94,7 +94,7 b' class _httprequesthandler(httpservermod.'
         try:
             self.do_hgweb()
         except socket.error as inst:
-            if inst[0] != errno.EPIPE:
+            if inst.errno != errno.EPIPE:
                 raise
 
     def do_POST(self):

mercurial/keepalive.py

@@ -636,7 +636,7 b' def safesend(self, str):'
             self.sentbytescount += len(str)
     except socket.error as v:
         reraise = True
-        if v[0] == errno.EPIPE:      # Broken pipe
+        if v.args[0] == errno.EPIPE:      # Broken pipe
             if self._HTTPConnection__state == httplib._CS_REQ_SENT:
                 self._broken_pipe_resp = None
                 self._broken_pipe_resp = self.getresponse()