fastannotate: slice strings to get single character

Behaves identically on Python 3 and Python 2.

Differential Revision: https://phab.mercurial-scm.org/D5612

hgext/fastannotate/formatter.py

@@ -103,7 +103,7 b' class defaultformatter(object):'
                         result += ': ' + self.ui.label('-' + lines[i],
                                                        'diff.deleted')
 
-            if result[-1] != '\n':
+            if result[-1:] != '\n':
                 result += '\n'
 
         self.ui.write(result)

hgext/fastannotate/protocol.py

@@ -98,7 +98,7 b' def _parseresponse(payload):'
     state = 0 # 0: vfspath, 1: size
     vfspath = size = ''
     while i < l:
-        ch = payload[i]
+        ch = payload[i:i + 1]
         if ch == '\0':
             if state == 1:
                 result[vfspath] = buffer(payload, i + 1, int(size))