Simplify setup.py

Pull out an Extension() helper and remove 2.6 support vestiges.

[rharwood@redhat.com: squashed, wrote commit message]

setup.py

@@ -5,6 +5,7 @@
 from setuptools import Distribution
 from setuptools.command.sdist import sdist
 from setuptools.extension import Extension
+import subprocess
 import platform
 import re
 import sys
@@ -28,20 +29,12 @@
               file=sys.stderr)
         SOURCE_EXT = 'c'
 
-get_output = None
 
-try:
-    import commands
-    get_output = commands.getoutput
-except ImportError:
-    import subprocess
+def get_output(*args, **kwargs):
+    res = subprocess.check_output(*args, shell=True, **kwargs)
+    decoded = res.decode('utf-8')
+    return decoded.strip()
 
-    def _get_output(*args, **kwargs):
-        res = subprocess.check_output(*args, shell=True, **kwargs)
-        decoded = res.decode('utf-8')
-        return decoded.strip()
-
-    get_output = _get_output
 
 # get the compile and link args
 link_args, compile_args = [
@@ -231,14 +224,25 @@ def ext_modules(self):
         del self._cythonized_ext_modules
 
 
+def make_extension(name_fmt, module, **kwargs):
+    """Helper method to remove the repetition in extension declarations."""
+    source = name_fmt.replace('.', '/') % module + '.' + SOURCE_EXT
+    if not os.path.exists(source):
+        raise OSError(source)
+    return Extension(
+        name_fmt % module,
+        extra_link_args=link_args,
+        extra_compile_args=compile_args,
+        library_dirs=library_dirs,
+        libraries=libraries,
+        sources=[source],
+        **kwargs
+    )
+
+
 # detect support
 def main_file(module):
-    return Extension('gssapi.raw.%s' % module,
-                     extra_link_args=link_args,
-                     extra_compile_args=compile_args,
-                     library_dirs=library_dirs,
-                     libraries=libraries,
-                     sources=['gssapi/raw/%s.%s' % (module, SOURCE_EXT)])
+    return make_extension('gssapi.raw.%s', module)
 
 
 ENUM_EXTS = []
@@ -248,43 +252,28 @@ def extension_file(module, canary):
     if ENABLE_SUPPORT_DETECTION and not hasattr(GSSAPI_LIB, canary):
         print('Skipping the %s extension because it '
               'is not supported by your GSSAPI implementation...' % module)
-        return None
-    else:
-        enum_ext_path = 'gssapi/raw/_enum_extensions/ext_%s.%s' % (module,
-                                                                   SOURCE_EXT)
-        if os.path.exists(enum_ext_path):
-            ENUM_EXTS.append(
-                Extension('gssapi.raw._enum_extensions.ext_%s' % module,
-                          extra_link_args=link_args,
-                          extra_compile_args=compile_args,
-                          sources=[enum_ext_path],
-                          library_dirs=library_dirs,
-                          libraries=libraries,
-                          include_dirs=['gssapi/raw/']))
-
-        return Extension('gssapi.raw.ext_%s' % module,
-                         extra_link_args=link_args,
-                         extra_compile_args=compile_args,
-                         library_dirs=library_dirs,
-                         libraries=libraries,
-                         sources=['gssapi/raw/ext_%s.%s' % (module,
-                                                            SOURCE_EXT)])
+        return
+
+    try:
+        ENUM_EXTS.append(
+            make_extension('gssapi.raw._enum_extensions.ext_%s', module,
+                           include_dirs=['gssapi/raw/'])
+        )
+    except OSError:
+        pass
+
+    return make_extension('gssapi.raw.ext_%s', module)
 
 
 def gssapi_modules(lst):
     # filter out missing files
     res = [mod for mod in lst if mod is not None]
 
     # add in supported mech files
-    MECHS_SUPPORTED = os.environ.get('GSSAPI_MECHS', 'krb5').split(',')
-    for mech in MECHS_SUPPORTED:
-        res.append(Extension('gssapi.raw.mech_%s' % mech,
-                             extra_link_args=link_args,
-                             extra_compile_args=compile_args,
-                             library_dirs=library_dirs,
-                             libraries=libraries,
-                             sources=['gssapi/raw/mech_%s.%s' % (mech,
-                                                                 SOURCE_EXT)]))
+    res.extend(
+        make_extension('gssapi.raw.mech_%s', mech)
+        for mech in os.environ.get('GSSAPI_MECHS', 'krb5').split(',')
+    )
 
     # add in any present enum extension files
     res.extend(ENUM_EXTS)