Python bindings src: PEP8 compliance

* import namespace clearance for src/*.py.
* Fixed a handful of is/is not None checks as well.

lang/python/src/__init__.py

@@ -95,7 +95,6 @@ GPGME documentation: https://www.gnupg.org/documentation/manuals/gpgme/
 """
 
 from __future__ import absolute_import, print_function, unicode_literals
-del absolute_import, print_function, unicode_literals
 
 from . import core
 from . import errors
@@ -106,6 +105,8 @@ from . import version
 from .core import Context
 from .core import Data
 
+del absolute_import, print_function, unicode_literals
+
 # Interface hygiene.
 
 # Drop the low-level gpgme that creeps in for some reason.

lang/python/src/callbacks.py

@@ -16,17 +16,18 @@
 #    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
 
 from __future__ import absolute_import, print_function, unicode_literals
-del absolute_import, print_function, unicode_literals
 
 from getpass import getpass
 
+del absolute_import, print_function, unicode_literals
+
 
 def passphrase_stdin(hint, desc, prev_bad, hook=None):
     """This is a sample callback that will read a passphrase from
     the terminal.  The hook here, if present, will be used to describe
     why the passphrase is needed."""
     why = ''
-    if hook != None:
+    if hook is not None:
         why = ' ' + hook
     if prev_bad:
         why += ' (again)'
@@ -35,7 +36,7 @@ def passphrase_stdin(hint, desc, prev_bad, hook=None):
 
 
 def progress_stdout(what, type, current, total, hook=None):
-    print("PROGRESS UPDATE: what = %s, type = %d, current = %d, total = %d" %\
+    print("PROGRESS UPDATE: what = %s, type = %d, current = %d, total = %d" %
           (what, type, current, total))
 
 

lang/python/src/core.py

@@ -1,7 +1,6 @@
 # -*- coding: utf-8 -*-
 
 from __future__ import absolute_import, print_function, unicode_literals
-del absolute_import, print_function, unicode_literals
 
 import re
 import os
@@ -14,6 +13,8 @@ from . import constants
 from . import errors
 from . import util
 
+del absolute_import, print_function, unicode_literals
+
 # Copyright (C) 2016-2018 g10 Code GmbH
 # Copyright (C) 2004, 2008 Igor Belyi <belyi@users.sourceforge.net>
 # Copyright (C) 2002 John Goerzen <jgoerzen@complete.org>

lang/python/src/errors.py

@@ -17,11 +17,12 @@
 #    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
 
 from __future__ import absolute_import, print_function, unicode_literals
-del absolute_import, print_function, unicode_literals
 
 from . import gpgme
 from . import util
 
+del absolute_import, print_function, unicode_literals
+
 # To appease static analysis tools, we define some constants here.
 # They are overwritten with the proper values by process_constants.
 NO_ERROR = None
@@ -64,33 +65,33 @@ class GpgError(Exception):
 
     @property
     def code(self):
-        if self.error == None:
+        if self.error is None:
             return None
         return gpgme.gpgme_err_code(self.error)
 
     @property
     def code_str(self):
-        if self.error == None:
+        if self.error is None:
             return None
         return gpgme.gpgme_strerror(self.error)
 
     @property
     def source(self):
-        if self.error == None:
+        if self.error is None:
             return None
         return gpgme.gpgme_err_source(self.error)
 
     @property
     def source_str(self):
-        if self.error == None:
+        if self.error is None:
             return None
         return gpgme.gpgme_strsource(self.error)
 
     def __str__(self):
         msgs = []
-        if self.context != None:
+        if self.context is not None:
             msgs.append(self.context)
-        if self.error != None:
+        if self.error is not None:
             msgs.append(self.source_str)
             msgs.append(self.code_str)
         return ': '.join(msgs)

lang/python/src/util.py

@@ -17,10 +17,11 @@
 #    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
 
 from __future__ import absolute_import, print_function, unicode_literals
-del absolute_import, print_function, unicode_literals
 
 import sys
 
+del absolute_import, print_function, unicode_literals
+
 
 def process_constants(prefix, scope):
     """Called by the constant modules to load up the constants from the C