make_app uses threading.Lock now by default

Uses keyword arguments to use multiprocessing or uwsgi mixin. This
fixes an issue on exotic *BSDs such as NetBSD where Python comes not
with inter-process semaphores (issue 3307):

     mod_wsgi (pid=14365): Target WSGI script '/var/www/vhosts/my.hostname.org/htdocs/isso.wsgi' cannot be loaded as Python module.
     mod_wsgi (pid=14365): Exception occurred processing WSGI script '/var/www/vhosts/my.hostname.org/htdocs/isso.wsgi'.
     Traceback (most recent call last):
       File "/var/www/vhosts/my.hostname.org/htdocs/isso.wsgi", line 8, in <module>
         application = make_app(Config.load("/var/www/vhosts/my.hostname.org/htdocs/isso.cfg"))
       File "/usr/pkg/lib/python2.7/site-packages/isso/__init__.py", line 155, in make_app
         isso = App(conf)
       File "/usr/pkg/lib/python2.7/site-packages/isso/__init__.py", line 91, in __init__
         super(Isso, self).__init__(conf)
       File "/usr/pkg/lib/python2.7/site-packages/isso/core.py", line 223, in __init__
         self.lock = multiprocessing.Lock()
       File "/usr/pkg/lib/python2.7/multiprocessing/__init__.py", line 175, in Lock
         from multiprocessing.synchronize import Lock
       File "/usr/pkg/lib/python2.7/multiprocessing/synchronize.py", line 59, in <module>
         " function, see issue 3770.")
     ImportError: This platform lacks a functioning sem_open implementation, therefore, the required synchronization primitives needed will not function, see issue 3770.

isso/__init__.py

@@ -30,16 +30,15 @@ from __future__ import print_function
 import pkg_resources
 dist = pkg_resources.get_distribution("isso")
 
-try:
-    import uwsgi
-except ImportError:
-    uwsgi = None
+# check if exectuable is `isso` and gevent is available
+import sys
+
+if sys.argv[0].startswith("isso"):
     try:
         import gevent.monkey; gevent.monkey.patch_all()
     except ImportError:
-        gevent = None
+        pass
 
-import sys
 import os
 import errno
 import logging
@@ -140,18 +139,20 @@ class Isso(object):
         return self.wsgi_app(environ, start_response)
 
 
-def make_app(conf=None):
+def make_app(conf=None, threading=True, multiprocessing=False, uwsgi=False):
 
-    if uwsgi:
-        class App(Isso, uWSGIMixin):
-            pass
-    elif gevent or sys.argv[0].endswith("isso"):
+    if threading:
         class App(Isso, ThreadedMixin):
             pass
-    else:
+
+    if multiprocessing:
         class App(Isso, ProcessMixin):
             pass
 
+    if uwsgi:
+        class App(Isso, uWSGIMixin):
+            pass
+
     isso = App(conf)
 
     for host in conf.getiter("general", "host"):

isso/run.py

@@ -5,4 +5,5 @@ import os
 from isso import make_app
 from isso.core import Config
 
-application = make_app(Config.load(os.environ.get('ISSO_SETTINGS')))
+application = make_app(Config.load(os.environ.get('ISSO_SETTINGS')),
+                       multiprocessing=True)