diff --git a/mercurial/changelog.py b/mercurial/changelog.py
--- a/mercurial/changelog.py
+++ b/mercurial/changelog.py
@@ -190,7 +190,7 @@ class changelogrevision(object):
 
         # The list of files may be empty. Which means nl3 is the first of the
         # double newline that precedes the description.
-        if text[nl3 + 1] == '\n':
+        if text[nl3 + 1:nl3 + 2] == '\n':
             doublenl = nl3
         else:
             doublenl = text.index('\n\n', nl3 + 1)
diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -491,10 +491,10 @@ def makefilename(repo, pat, node, desc=N
         patlen = len(pat)
         i = 0
         while i < patlen:
-            c = pat[i]
+            c = pat[i:i + 1]
             if c == '%':
                 i += 1
-                c = pat[i]
+                c = pat[i:i + 1]
                 c = expander[c]()
             newname.append(c)
             i += 1
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -1980,13 +1980,13 @@ def parsedate(date, formats=None, bias=N
             # this piece is for rounding the specific end of unknowns
             b = bias.get(part)
             if b is None:
-                if part[0] in "HMS":
+                if part[0:1] in "HMS":
                     b = "00"
                 else:
                     b = "0"
 
             # this piece is for matching the generic end to today's date
-            n = datestr(now, "%" + part[0])
+            n = datestr(now, "%" + part[0:1])
 
             defaults[part] = (b, n)