util: move common proxyobserver attributes to the base class

util: move common proxyobserver attributes to the base class

Fixes the following pytype warnings:

    line 791, in _writedata: No attribute 'logdata' on baseproxyobserver [attribute-error]
    line 792, in _writedata: No attribute 'logdataapis' on baseproxyobserver [attribute-error]
    line 793, in _writedata: No attribute 'fh' on baseproxyobserver [attribute-error]
    line 794, in _writedata: No attribute 'fh' on baseproxyobserver [attribute-error]
    line 799, in _writedata: No attribute 'logdataapis' on baseproxyobserver [attribute-error]
    line 800, in _writedata: No attribute 'fh' on baseproxyobserver [attribute-error]
    line 802, in _writedata: No attribute 'fh' on baseproxyobserver [attribute-error]
    line 803, in _writedata: No attribute 'name' on baseproxyobserver [attribute-error]
    line 805, in _writedata: No attribute 'fh' on baseproxyobserver [attribute-error]
    line 809, in _writedata: No attribute 'logdataapis' on baseproxyobserver [attribute-error]
    line 810, in _writedata: No attribute 'fh' on baseproxyobserver [attribute-error]
    line 814, in _writedata: No attribute 'fh' on baseproxyobserver [attribute-error]
    line 815, in _writedata: No attribute 'name' on baseproxyobserver [attribute-error]
    line 817, in _writedata: No attribute 'fh' on baseproxyobserver [attribute-error]

Differential Revision: https://phab.mercurial-scm.org/D7675

--- a/mercurial/util.py	Wed Dec 11 22:23:42 2019 -0800
+++ b/mercurial/util.py	Sun Dec 15 21:34:00 2019 -0500
@@ -787,6 +787,12 @@
 
 
 class baseproxyobserver(object):
+    def __init__(self, fh, name, logdata, logdataapis):
+        self.fh = fh
+        self.name = name
+        self.logdata = logdata
+        self.logdataapis = logdataapis
+
     def _writedata(self, data):
         if not self.logdata:
             if self.logdataapis:
@@ -823,10 +829,7 @@
     def __init__(
         self, fh, name, reads=True, writes=True, logdata=False, logdataapis=True
     ):
-        self.fh = fh
-        self.name = name
-        self.logdata = logdata
-        self.logdataapis = logdataapis
+        super(fileobjectobserver, self).__init__(fh, name, logdata, logdataapis)
         self.reads = reads
         self.writes = writes
 
@@ -949,13 +952,10 @@
         logdata=False,
         logdataapis=True,
     ):
-        self.fh = fh
-        self.name = name
+        super(socketobserver, self).__init__(fh, name, logdata, logdataapis)
         self.reads = reads
         self.writes = writes
         self.states = states
-        self.logdata = logdata
-        self.logdataapis = logdataapis
 
     def makefile(self, res, mode=None, bufsize=None):
         if not self.states: