require Mercurial 1.3 again (how did that get dropped?)

avoid deprecation warning about os.popen3

R=r
http://go/go-review/1026018

lib/codereview/codereview.py

@@ -51,6 +51,28 @@ except:
 	from mercurial.version import version as v
 	hgversion = v.get_version()
 
+oldMessage = """
+The code review extension requires Mercurial 1.3 or newer.
+
+To install a new Mercurial,
+
+	sudo easy_install mercurial
+
+works on most systems.
+"""
+
+linuxMessage = """
+You may need to clear your current Mercurial installation by running:
+
+	sudo apt-get remove mercurial mercurial-common
+	sudo rm -rf /etc/mercurial
+"""
+
+if hgversion < '1.3':
+	msg = oldMessage
+	if os.access("/etc/mercurial", 0):
+		msg += linuxMessage
+	raise util.Abort(msg)
 
 # To experiment with Mercurial in the python interpreter:
 #    >>> repo = hg.repository(ui.ui(), path = ".")
@@ -584,12 +606,13 @@ def CheckGofmt(ui, repo, files, just_warn=False):
 	cwd = os.getcwd()
 	files = [RelativePath(repo.root + '/' + f, cwd) for f in files]
 	try:
-		stdin, stdout, stderr = os.popen3(["gofmt", "-l"] + files)
-		stdin.close()
+		cmd = subprocess.Popen(["gofmt", "-l"] + files, shell=False, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, close_fds=True)
+		cmd.stdin.close()
 	except:
 		raise util.Abort("gofmt: " + ExceptionDetail())
-	data = stdout.read()
-	errors = stderr.read()
+	data = cmd.stdout.read()
+	errors = cmd.stderr.read()
+	cmd.wait()
 	if len(errors) > 0:
 		ui.warn("gofmt errors:\n" + errors.rstrip() + "\n")
 		return