Modernize the code now that Python 2.5 is no longer supported

- Use print function instead of print statement;
- Use new exception handling;
- Use in operator instead of has_key();
- Do not use tuple arguments in functions;
- Other miscellaneous improvements.

This is based on output of `futurize --stage1`, with some
manual corrections.

utils/check_sources.py

@@ -10,6 +10,7 @@
     :copyright: Copyright 2007-2013 by the Sphinx team, see AUTHORS.
     :license: BSD, see LICENSE for details.
 """
+from __future__ import print_function
 
 import sys, os, re
 import cStringIO
@@ -54,7 +55,7 @@ if sys.version_info < (3, 0):
     def check_syntax(fn, lines):
         try:
             compile(b('').join(lines), fn, "exec")
-        except SyntaxError, err:
+        except SyntaxError as err:
             yield 0, "not compilable: %s" % err
 
 
@@ -77,9 +78,9 @@ def check_style_and_encoding(fn, lines):
             yield lno+1, 'using == None/True/False'
         try:
             line.decode(encoding)
-        except UnicodeDecodeError, err:
+        except UnicodeDecodeError as err:
             yield lno+1, "not decodable: %s\n   Line: %r" % (err, line)
-        except LookupError, err:
+        except LookupError as err:
             yield 0, "unknown encoding: %s" % encoding
             encoding = 'latin1'
 
@@ -183,7 +184,7 @@ def main(argv):
     elif len(args) == 1:
         path = args[0]
     else:
-        print args
+        print(args)
         parser.error('No more then one path supported')
 
     verbose = options.verbose
@@ -214,7 +215,7 @@ def main(argv):
                 continue
 
             if verbose:
-                print "Checking %s..." % fn
+                print("Checking %s..." % fn)
 
             try:
                 f = open(fn, 'rb')
@@ -222,8 +223,8 @@ def main(argv):
                     lines = list(f)
                 finally:
                     f.close()
-            except (IOError, OSError), err:
-                print "%s: cannot open: %s" % (fn, err)
+            except (IOError, OSError) as err:
+                print("%s: cannot open: %s" % (fn, err))
                 num += 1
                 continue
 
@@ -231,15 +232,15 @@ def main(argv):
                 if not in_check_pkg and checker.only_pkg:
                     continue
                 for lno, msg in checker(fn, lines):
-                    print >>out, "%s:%d: %s" % (fn, lno, msg)
+                    print("%s:%d: %s" % (fn, lno, msg), file=out)
                     num += 1
     if verbose:
-        print
+        print()
     if num == 0:
-        print "No errors found."
+        print("No errors found.")
     else:
-        print out.getvalue().rstrip('\n')
-        print "%d error%s found." % (num, num > 1 and "s" or "")
+        print(out.getvalue().rstrip('\n'))
+        print("%d error%s found." % (num, num > 1 and "s" or ""))
     return int(num > 0)