Always use the same name for the exception defined in this module!

Error reported via email by Pete Shinners <pete@visionart.com>.

Fixed some indentation inconsistencies.

Lib/zipfile.py

@@ -10,9 +10,9 @@ try:
 except:
     zlib = None
 
-class _BadZipfile(Exception):
+class BadZipfile(Exception):
     pass
-error = _BadZipfile	# The exception raised by this module
+error = BadZipfile	# The exception raised by this module
 
 # constants for Zip file compression methods
 ZIP_STORED = 0
@@ -180,7 +180,7 @@ class ZipFile:
             fname = fp.read(fheader[10])
             if fname != data.filename:
                 raise RuntimeError, \
- 'File name in Central Directory "%s" and File Header "%s" differ.' % (
+                      'File name in directory "%s" and header "%s" differ.' % (
                           data.filename, fname)
 
     def namelist(self):