diff -r 57875cf423c9 -r 2372284d9457 mercurial/pure/bdiff.py
--- a/mercurial/pure/bdiff.py	Sat Oct 05 10:29:34 2019 -0400
+++ b/mercurial/pure/bdiff.py	Sun Oct 06 09:45:02 2019 -0400
@@ -11,6 +11,7 @@
 import re
 import struct
 
+
 def splitnewlines(text):
     '''like str.splitlines, but only split on newlines.'''
     lines = [l + '\n' for l in text.split('\n')]
@@ -21,6 +22,7 @@
             lines[-1] = lines[-1][:-1]
     return lines
 
+
 def _normalizeblocks(a, b, blocks):
     prev = None
     r = []
@@ -38,18 +40,21 @@
         a2end = a2 + l2
         b2end = b2 + l2
         if a1end == a2:
-            while (a1end + shift < a2end and
-                   a[a1end + shift] == b[b1end + shift]):
+            while (
+                a1end + shift < a2end and a[a1end + shift] == b[b1end + shift]
+            ):
                 shift += 1
         elif b1end == b2:
-            while (b1end + shift < b2end and
-                   a[a1end + shift] == b[b1end + shift]):
+            while (
+                b1end + shift < b2end and a[a1end + shift] == b[b1end + shift]
+            ):
                 shift += 1
         r.append((a1, b1, l1 + shift))
         prev = a2 + shift, b2 + shift, l2 - shift
     r.append(prev)
     return r
 
+
 def bdiff(a, b):
     a = bytes(a).splitlines(True)
     b = bytes(b).splitlines(True)
@@ -76,6 +81,7 @@
 
     return "".join(bin)
 
+
 def blocks(a, b):
     an = splitnewlines(a)
     bn = splitnewlines(b)
@@ -83,6 +89,7 @@
     d = _normalizeblocks(an, bn, d)
     return [(i, i + n, j, j + n) for (i, j, n) in d]
 
+
 def fixws(text, allws):
     if allws:
         text = re.sub('[ \t\r]+', '', text)