Clean up some code in cython.inline() implementation.

Cython/Build/Inline.py

 from __future__ import absolute_import
 
-import sys, os, re, inspect
-import imp
-
-try:
-    import hashlib
-except ImportError:
-    import md5 as hashlib
+import hashlib
+import inspect
+import os
+import re
+import sys
 
 from distutils.core import Distribution, Extension
 from distutils.command.build_ext import build_ext
 
 import Cython
-from ..Compiler.Main import Context, CompilationOptions, default_options
+from ..Compiler.Main import Context, default_options
 
 from ..Compiler.Visitor import CythonTransform, EnvTransform
 from ..Compiler.ParseTreeTransforms import SkipDeclarations
 from ..Compiler.TreeFragment import parse_from_strings
 from ..Compiler.StringEncoding import _unicode
 from .Dependencies import strip_string_literals, cythonize, cached_function
-from ..Compiler import Pipeline, Nodes
+from ..Compiler import Pipeline
 from ..Utils import get_cython_cache_dir
 import cython as cython_module
 
-IS_PY3 = sys.version_info >= (3, 0)
+
+IS_PY3 = sys.version_info >= (3,)
 
 # A utility function to convert user-supplied ASCII strings to unicode.
-if sys.version_info[0] < 3:
+if not IS_PY3:
     def to_unicode(s):
         if isinstance(s, bytes):
             return s.decode('ascii')
@@ -132,6 +131,7 @@ def _create_context(cython_include_dirs):
 _cython_inline_cache = {}
 _cython_inline_default_context = _create_context(('.',))
 
+
 def _populate_unbound(kwds, unbound_symbols, locals=None, globals=None):
     for symbol in unbound_symbols:
         if symbol not in kwds:
@@ -148,10 +148,12 @@ def _populate_unbound(kwds, unbound_symbols, locals=None, globals=None):
             else:
                 print("Couldn't find %r" % symbol)
 
+
 def _inline_key(orig_code, arg_sigs, language_level):
     key = orig_code, arg_sigs, sys.version_info, sys.executable, language_level, Cython.__version__
     return hashlib.sha1(_unicode(key).encode('utf-8')).hexdigest()
 
+
 def cython_inline(code, get_type=unsafe_type,
                   lib_dir=os.path.join(get_cython_cache_dir(), 'inline'),
                   cython_include_dirs=None, cython_compiler_directives=None,
@@ -161,7 +163,7 @@ def cython_inline(code, get_type=unsafe_type,
         get_type = lambda x: 'object'
     ctx = _create_context(tuple(cython_include_dirs)) if cython_include_dirs else _cython_inline_default_context
 
-    cython_compiler_directives = dict(cython_compiler_directives or {})
+    cython_compiler_directives = dict(cython_compiler_directives) if cython_compiler_directives else {}
     if language_level is None and 'language_level' not in cython_compiler_directives:
         language_level = '3str'
     if language_level is not None:
@@ -274,6 +276,7 @@ def __invoke(%(params)s):
     arg_list = [kwds[arg] for arg in arg_names]
     return module.__invoke(*arg_list)
 
+
 # Cached suffix used by cython_inline above.  None should get
 # overridden with actual value upon the first cython_inline invocation
 cython_inline.so_ext = None