--- a/mercurial/commandserver.py	Sat Oct 05 10:29:34 2019 -0400
+++ b/mercurial/commandserver.py	Sun Oct 06 09:45:02 2019 -0400
@@ -18,6 +18,7 @@
 
 try:
     import selectors
+
     selectors.BaseSelector
 except ImportError:
     from .thirdparty import selectors2 as selectors
@@ -37,6 +38,7 @@
     procutil,
 )
 
+
 class channeledoutput(object):
     """
     Write data to out in the following format:
@@ -44,6 +46,7 @@
     data length (unsigned int),
     data
     """
+
     def __init__(self, out, channel):
         self.out = out
         self.channel = channel
@@ -64,6 +67,7 @@
             raise AttributeError(attr)
         return getattr(self.out, attr)
 
+
 class channeledmessage(object):
     """
     Write encoded message and metadata to out in the following format:
@@ -92,6 +96,7 @@
     def __getattr__(self, attr):
         return getattr(self._cout, attr)
 
+
 class channeledinput(object):
     """
     Read data from in_.
@@ -178,10 +183,12 @@
             raise AttributeError(attr)
         return getattr(self.in_, attr)
 
+
 _messageencoders = {
     b'cbor': lambda v: b''.join(cborutil.streamencode(v)),
 }
 
+
 def _selectmessageencoder(ui):
     # experimental config: cmdserver.message-encodings
     encnames = ui.configlist(b'cmdserver', b'message-encodings')
@@ -189,14 +196,17 @@
         f = _messageencoders.get(n)
         if f:
             return n, f
-    raise error.Abort(b'no supported message encodings: %s'
-                      % b' '.join(encnames))
+    raise error.Abort(
+        b'no supported message encodings: %s' % b' '.join(encnames)
+    )
+
 
 class server(object):
     """
     Listens for commands on fin, runs them and writes the output on a channel
     based stream to fout.
     """
+
     def __init__(self, ui, repo, fin, fout, prereposetups=None):
         self.cwd = encoding.getcwd()
 
@@ -282,7 +292,7 @@
             self.repo.baseui = copiedui
             # clone ui without using ui.copy because this is protected
             repoui = self.repoui.__class__(self.repoui)
-            repoui.copy = copiedui.copy # redo copy protection
+            repoui.copy = copiedui.copy  # redo copy protection
             uis.append(repoui)
             self.repo.ui = self.repo.dirstate._ui = repoui
             self.repo.invalidateall()
@@ -295,9 +305,16 @@
             if not util.safehasattr(self.cin, 'fileno'):
                 ui.setconfig('ui', 'nontty', 'true', 'commandserver')
 
-        req = dispatch.request(args[:], copiedui, self.repo, self.cin,
-                               self.cout, self.cerr, self.cmsg,
-                               prereposetups=self._prereposetups)
+        req = dispatch.request(
+            args[:],
+            copiedui,
+            self.repo,
+            self.cin,
+            self.cout,
+            self.cerr,
+            self.cmsg,
+            prereposetups=self._prereposetups,
+        )
 
         try:
             ret = dispatch.dispatch(req) & 255
@@ -324,8 +341,7 @@
 
         return cmd != ''
 
-    capabilities = {'runcommand': runcommand,
-                    'getencoding': getencoding}
+    capabilities = {'runcommand': runcommand, 'getencoding': getencoding}
 
     def serve(self):
         hellomsg = 'capabilities: ' + ' '.join(sorted(self.capabilities))
@@ -352,6 +368,7 @@
 
         return 0
 
+
 def setuplogging(ui, repo=None, fp=None):
     """Set up server logging facility
 
@@ -377,8 +394,13 @@
         # developer config: cmdserver.max-log-size
         maxsize = ui.configbytes(b'cmdserver', b'max-log-size')
         vfs = vfsmod.vfs(os.path.dirname(logpath))
-        logger = loggingutil.filelogger(vfs, os.path.basename(logpath), tracked,
-                                        maxfiles=maxfiles, maxsize=maxsize)
+        logger = loggingutil.filelogger(
+            vfs,
+            os.path.basename(logpath),
+            tracked,
+            maxfiles=maxfiles,
+            maxsize=maxsize,
+        )
 
     targetuis = {ui}
     if repo:
@@ -387,6 +409,7 @@
     for u in targetuis:
         u.setlogger(b'cmdserver', logger)
 
+
 class pipeservice(object):
     def __init__(self, ui, repo, opts):
         self.ui = ui
@@ -406,6 +429,7 @@
             finally:
                 sv.cleanup()
 
+
 def _initworkerprocess():
     # use a different process group from the master process, in order to:
     # 1. make the current process group no longer "orphaned" (because the
@@ -423,6 +447,7 @@
     # same state inherited from parent.
     random.seed()
 
+
 def _serverequest(ui, repo, conn, createcmdserver, prereposetups):
     fin = conn.makefile(r'rb')
     fout = conn.makefile(r'wb')
@@ -442,7 +467,7 @@
             pass
         finally:
             sv.cleanup()
-    except: # re-raises
+    except:  # re-raises
         # also write traceback to error channel. otherwise client cannot
         # see it because it is written to server's stderr by default.
         if sv:
@@ -459,6 +484,7 @@
             if inst.errno != errno.EPIPE:
                 raise
 
+
 class unixservicehandler(object):
     """Set of pluggable operations for unix-mode services
 
@@ -492,6 +518,7 @@
         serves for the current connection"""
         return server(self.ui, repo, fin, fout, prereposetups)
 
+
 class unixforkingservice(object):
     """
     Listens on unix domain socket and forks server per connection
@@ -558,10 +585,12 @@
         exiting = False
         h = self._servicehandler
         selector = selectors.DefaultSelector()
-        selector.register(self._sock, selectors.EVENT_READ,
-                          self._acceptnewconnection)
-        selector.register(self._mainipc, selectors.EVENT_READ,
-                          self._handlemainipc)
+        selector.register(
+            self._sock, selectors.EVENT_READ, self._acceptnewconnection
+        )
+        selector.register(
+            self._mainipc, selectors.EVENT_READ, self._handlemainipc
+        )
         while True:
             if not exiting and h.shouldexit():
                 # clients can no longer connect() to the domain socket, so
@@ -605,8 +634,9 @@
         pid = os.fork()
         if pid:
             try:
-                self.ui.log(b'cmdserver', b'forked worker process (pid=%d)\n',
-                            pid)
+                self.ui.log(
+                    b'cmdserver', b'forked worker process (pid=%d)\n', pid
+                )
                 self._workerpids.add(pid)
                 h.newconnection()
             finally:
@@ -662,8 +692,13 @@
         _initworkerprocess()
         h = self._servicehandler
         try:
-            _serverequest(self.ui, self.repo, conn, h.createcmdserver,
-                          prereposetups=[self._reposetup])
+            _serverequest(
+                self.ui,
+                self.repo,
+                conn,
+                h.createcmdserver,
+                prereposetups=[self._reposetup],
+            )
         finally:
             gc.collect()  # trigger __del__ since worker process uses os._exit
 
@@ -677,8 +712,9 @@
                 try:
                     self._cmdserveripc.send(self.root)
                 except socket.error:
-                    self.ui.log(b'cmdserver',
-                                b'failed to send repo root to master\n')
+                    self.ui.log(
+                        b'cmdserver', b'failed to send repo root to master\n'
+                    )
 
         repo.__class__ = unixcmdserverrepo
         repo._cmdserveripc = self._workeripc