Detect binary output file (txt/html)

Printing out bytes values to text destination results in mangled
output. Add better detection.

Closes-bug: 1613169
Co-Authored-By: Ian Cordasco <graffatcolmingov@gmail.com>
Change-Id: I6e08cea789e13b71f6e70fbe991026b75be80199

bandit/formatters/html.py

@@ -152,6 +152,7 @@ import sys
 
 from bandit.core import docs_utils
 from bandit.core import test_properties
+from bandit.formatters import utils
 
 LOG = logging.getLogger(__name__)
 
@@ -372,8 +373,9 @@ pre {
                                           results=results_str)
 
     with fileobj:
-        fileobj.write(str(header_block.encode('utf-8')))
-        fileobj.write(str(report_contents.encode('utf-8')))
+        wrapped_file = utils.wrap_file_object(fileobj)
+        wrapped_file.write(utils.convert_file_contents(header_block))
+        wrapped_file.write(utils.convert_file_contents(report_contents))
 
     if fileobj.name != sys.stdout.name:
         LOG.info("HTML output written to file: %s", fileobj.name)

bandit/formatters/text.py

@@ -45,6 +45,7 @@ import sys
 
 from bandit.core import constants
 from bandit.core import test_properties
+from bandit.formatters import utils
 
 LOG = logging.getLogger(__name__)
 
@@ -155,7 +156,8 @@ def report(manager, fileobj, sev_level, conf_level, lines=-1):
     result = '\n'.join([bit for bit in bits]) + '\n'
 
     with fileobj:
-        fileobj.write(str(result.encode('utf-8')))
+        wrapped_file = utils.wrap_file_object(fileobj)
+        wrapped_file.write(utils.convert_file_contents(result))
 
     if fileobj.name != sys.stdout.name:
         LOG.info("Text output written to file: %s", fileobj.name)

bandit/formatters/utils.py

@@ -0,0 +1,43 @@
+# Copyright (c) 2016 Rackspace, Inc.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License"); you may
+#  not use this file except in compliance with the License. You may obtain
+#  a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#  License for the specific language governing permissions and limitations
+#  under the License.
+"""Utility functions for formatting plugins for Bandit."""
+
+import io
+
+import six
+
+
+def wrap_file_object(fileobj):
+    """Handle differences in Python 2 and 3 around writing bytes."""
+    # If it's not an instance of IOBase, we're probably using Python 2 and
+    # that is less finnicky about writing text versus bytes to a file.
+    if not isinstance(fileobj, io.IOBase):
+        return fileobj
+
+    # At this point we're using Python 3 and that will mangle text written to
+    # a file written in bytes mode. So, let's check if the file can handle
+    # text as opposed to bytes.
+    if isinstance(fileobj, io.TextIOBase):
+        return fileobj
+
+    # Finally, we've determined that the fileobj passed in cannot handle text,
+    # so we use TextIOWrapper to handle the conversion for us.
+    return io.TextIOWrapper(fileobj)
+
+
+def convert_file_contents(text):
+    """Convert text to built-in strings on Python 2."""
+    if not six.PY2:
+        return text
+    return str(text.encode('utf-8'))