Remove support for gzipped files in load_json_file

Compression related functions were removed from securesystemslib as it was
deemed more appropriate for callers to handle compression/decompression at
a different level. However, the automatic decompression functionality in
load_json_file() had remained.

Remove that change and tidy up load_json_file() to only close the
fileobject once. Since Python 2.5 a finally block is always called,
regardless of whether there is an exception or not. Therefore there's no
need to close the fileobject in the else block and the finally block.

Signed-off-by: Joshua Lock <jlock@vmware.com>

securesystemslib/util.py

@@ -26,7 +26,6 @@
 from __future__ import unicode_literals
 
 import os
-import gzip
 import shutil
 import logging
 import tempfile
@@ -327,15 +326,7 @@ def load_json_file(filepath):
   securesystemslib.formats.PATH_SCHEMA.check_match(filepath)
 
   deserialized_object = None
-
-  # The file is mostly likely gzipped.
-  if filepath.endswith('.gz'):
-    logger.debug('gzip.open(' + str(filepath) + ')')
-    fileobject = six.StringIO(gzip.open(filepath).read().decode('utf-8'))
-
-  else:
-    logger.debug('open(' + str(filepath) + ')')
-    fileobject = open(filepath)
+  fileobject = open(filepath)
 
   try:
     deserialized_object = json.load(fileobject)
@@ -345,7 +336,6 @@ def load_json_file(filepath):
       ' Python object: ' + repr(filepath))
 
   else:
-    fileobject.close()
     return deserialized_object
 
   finally:

tests/test_util.py

@@ -27,7 +27,6 @@
 
 import os
 import sys
-import gzip
 import shutil
 import logging
 import tempfile
@@ -57,30 +56,6 @@ def tearDown(self):
 
 
 
-  def _compress_existing_file(self, filepath):
-    """
-    [Helper]Compresses file 'filepath' and returns file path of
-    the compresses file.
-    """
-
-    # NOTE: DO NOT forget to remove the newly created compressed file!
-    if os.path.exists(filepath):
-      compressed_filepath = filepath+'.gz'
-      f_in = open(filepath, 'rb')
-      f_out = gzip.open(compressed_filepath, 'wb')
-      f_out.writelines(f_in)
-      f_out.close()
-      f_in.close()
-
-      return compressed_filepath
-
-    else:
-      logger.error('Compression of ' + repr(filepath)  +' failed.'
-          '  Path does not exist.')
-      sys.exit(1)
-
-
-
   def test_B1_get_file_details(self):
     # Goal: Verify proper output given certain expected/unexpected input.
 
@@ -190,11 +165,6 @@ def  test_B6_load_json_file(self):
     fileobj.close()
     self.assertEqual(data, securesystemslib.util.load_json_file(filepath))
 
-    # Test a gzipped file.
-    compressed_filepath = self._compress_existing_file(filepath)
-    self.assertEqual(data,
-        securesystemslib.util.load_json_file(compressed_filepath))
-
     # Improperly formatted arguments.
     for bogus_arg in [1, [b'a'], {'a':b'b'}]:
       self.assertRaises(securesystemslib.exceptions.FormatError,