diff --git a/hgext/blackbox.py b/hgext/blackbox.py
--- a/hgext/blackbox.py
+++ b/hgext/blackbox.py
@@ -190,7 +190,7 @@
             break
 
         # count the commands by matching lines like: 2013/01/23 19:13:36 root>
-        if re.match('^\d{4}/\d{2}/\d{2} \d{2}:\d{2}:\d{2} .*> .*', line):
+        if re.match(br'^\d{4}/\d{2}/\d{2} \d{2}:\d{2}:\d{2} .*> .*', line):
             count += 1
         output.append(line)
 
diff --git a/hgext/commitextras.py b/hgext/commitextras.py
--- a/hgext/commitextras.py
+++ b/hgext/commitextras.py
@@ -58,7 +58,7 @@
                 if not k:
                     msg = _("unable to parse '%s', keys can't be empty")
                     raise error.Abort(msg % raw)
-                if re.search('[^\w-]', k):
+                if re.search(br'[^\w-]', k):
                     msg = _("keys can only contain ascii letters, digits,"
                             " '_' and '-'")
                     raise error.Abort(msg)
diff --git a/hgext/convert/cvsps.py b/hgext/convert/cvsps.py
--- a/hgext/convert/cvsps.py
+++ b/hgext/convert/cvsps.py
@@ -122,7 +122,7 @@
     re_31 = re.compile(b'----------------------------$')
     re_32 = re.compile(b'======================================='
                        b'======================================$')
-    re_50 = re.compile(b'revision ([\\d.]+)(\s+locked by:\s+.+;)?$')
+    re_50 = re.compile(br'revision ([\d.]+)(\s+locked by:\s+.+;)?$')
     re_60 = re.compile(br'date:\s+(.+);\s+author:\s+(.+);\s+state:\s+(.+?);'
                        br'(\s+lines:\s+(\+\d+)?\s+(-\d+)?;)?'
                        br'(\s+commitid:\s+([^;]+);)?'
diff --git a/hgext/mq.py b/hgext/mq.py
--- a/hgext/mq.py
+++ b/hgext/mq.py
@@ -1181,7 +1181,7 @@
     def makepatchname(self, title, fallbackname):
         """Return a suitable filename for title, adding a suffix to make
         it unique in the existing list"""
-        namebase = re.sub('[\s\W_]+', '_', title.lower()).strip('_')
+        namebase = re.sub(br'[\s\W_]+', b'_', title.lower()).strip(b'_')
         namebase = namebase[:75] # avoid too long name (issue5117)
         if namebase:
             try:
diff --git a/hgext/phabricator.py b/hgext/phabricator.py
--- a/hgext/phabricator.py
+++ b/hgext/phabricator.py
@@ -255,9 +255,9 @@
     repo.ui.setconfig(b'phabricator', b'repophid', repophid)
     return repophid
 
-_differentialrevisiontagre = re.compile(b'\AD([1-9][0-9]*)\Z')
+_differentialrevisiontagre = re.compile(br'\AD([1-9][0-9]*)\Z')
 _differentialrevisiondescre = re.compile(
-    b'^Differential Revision:\s*(?P<url>(?:.*)D(?P<id>[1-9][0-9]*))$', re.M)
+    br'^Differential Revision:\s*(?P<url>(?:.*)D(?P<id>[1-9][0-9]*))$', re.M)
 
 def getoldnodedrevmap(repo, nodelist):
     """find previous nodes that has been sent to Phabricator
diff --git a/hgext/releasenotes.py b/hgext/releasenotes.py
--- a/hgext/releasenotes.py
+++ b/hgext/releasenotes.py
@@ -55,7 +55,7 @@
     ('api', _('API Changes')),
 ]
 
-RE_DIRECTIVE = re.compile('^\.\. ([a-zA-Z0-9_]+)::\s*([^$]+)?$')
+RE_DIRECTIVE = re.compile(br'^\.\. ([a-zA-Z0-9_]+)::\s*([^$]+)?$')
 RE_ISSUE = br'\bissue ?[0-9]{4,6}(?![0-9])\b'
 
 BULLET_SECTION = _('Other Changes')
diff --git a/mercurial/color.py b/mercurial/color.py
--- a/mercurial/color.py
+++ b/mercurial/color.py
@@ -484,7 +484,7 @@
             w32effects = None
         else:
             origattr = csbi.wAttributes
-            ansire = re.compile(b'\033\[([^m]*)m([^\033]*)(.*)',
+            ansire = re.compile(br'\033\[([^m]*)m([^\033]*)(.*)',
                                 re.MULTILINE | re.DOTALL)
 
     def win32print(ui, writefunc, text, **opts):
diff --git a/mercurial/patch.py b/mercurial/patch.py
--- a/mercurial/patch.py
+++ b/mercurial/patch.py
@@ -638,8 +638,8 @@
         return self.changed | self.removed
 
 # @@ -start,len +start,len @@ or @@ -start +start @@ if len is 1
-unidesc = re.compile('@@ -(\d+)(?:,(\d+))? \+(\d+)(?:,(\d+))? @@')
-contextdesc = re.compile('(?:---|\*\*\*) (\d+)(?:,(\d+))? (?:---|\*\*\*)')
+unidesc = re.compile(br'@@ -(\d+)(?:,(\d+))? \+(\d+)(?:,(\d+))? @@')
+contextdesc = re.compile(br'(?:---|\*\*\*) (\d+)(?:,(\d+))? (?:---|\*\*\*)')
 eolmodes = ['strict', 'crlf', 'lf', 'auto']
 
 class patchfile(object):
@@ -2762,7 +2762,7 @@
     return maxfile, maxtotal, addtotal, removetotal, binary
 
 def diffstatdata(lines):
-    diffre = re.compile('^diff .*-r [a-z0-9]+\s(.*)$')
+    diffre = re.compile(br'^diff .*-r [a-z0-9]+\s(.*)$')
 
     results = []
     filename, adds, removes, isbinary = None, 0, 0, False