Replace backticks with repr() or "%r"

From SF patch #852334.
diff --git a/Tools/scripts/checkappend.py b/Tools/scripts/checkappend.py
index b3141df..a8714d9 100755
--- a/Tools/scripts/checkappend.py
+++ b/Tools/scripts/checkappend.py
@@ -65,7 +65,7 @@
 def check(file):
     if os.path.isdir(file) and not os.path.islink(file):
         if verbose:
-            print "%s: listing directory" % `file`
+            print "%r: listing directory" % (file,)
         names = os.listdir(file)
         for name in names:
             fullname = os.path.join(file, name)
@@ -78,15 +78,15 @@
     try:
         f = open(file)
     except IOError, msg:
-        errprint("%s: I/O Error: %s" % (`file`, str(msg)))
+        errprint("%r: I/O Error: %s" % (file, msg))
         return
 
     if verbose > 1:
-        print "checking", `file`, "..."
+        print "checking %r ..." % (file,)
 
     ok = AppendChecker(file, f).run()
     if verbose and ok:
-        print "%s: Clean bill of health." % `file`
+        print "%r: Clean bill of health." % (file,)
 
 [FIND_DOT,
  FIND_APPEND,
@@ -105,7 +105,7 @@
         try:
             tokenize.tokenize(self.file.readline, self.tokeneater)
         except tokenize.TokenError, msg:
-            errprint("%s: Token Error: %s" % (`self.fname`, str(msg)))
+            errprint("%r: Token Error: %s" % (self.fname, msg))
             self.nerrors = self.nerrors + 1
         return self.nerrors == 0
 
@@ -159,7 +159,7 @@
                 state = FIND_DOT
 
         else:
-            raise SystemError("unknown internal state '%s'" % `state`)
+            raise SystemError("unknown internal state '%r'" % (state,))
 
         self.state = state