Add GIL lock to pprotect python code.

This is part 2 of fix to bug opencog/atomspace#671

opencog/cogserver/modules/python/PythonModule.cc

@@ -73,13 +73,19 @@ static bool already_loaded = false;
 PythonModule::~PythonModule()
 {
     logger().info("[PythonModule] destructor");
+
+    PyGILState_STATE gstate;
+    gstate = PyGILState_Ensure();
+
     unregisterAgentsAndRequests();
     do_load_py_unregister();
 
     for (PythonAgentFactory* af : _agentFactories) delete af;
     for (PythonRequestFactory* rf : _requestFactories) delete rf;
 
     already_loaded = false;
+
+    PyGILState_Release(gstate);
 }
 
 bool PythonModule::unregisterAgentsAndRequests()
@@ -113,11 +119,15 @@ void PythonModule::init()
                     "Python not initialized, missing global_python_init()");
     }
 
+    PyGILState_STATE gstate;
+    gstate = PyGILState_Ensure();
+
     // Many python libraries (e.g. ROS) expect sys.argv to be set. So,
     // avoid the error print, and let them know who we are.
     static const char *argv0 = "cogserver";
     PySys_SetArgv(1, (char **) &argv0);
 
+
     // NOTE: Even though the Cython docs do not say that you need to call this
     // more than once, you need to call the import functions in each separate
     // shared library that accesses Cython defined api. If you don't then you
@@ -138,6 +148,8 @@ void PythonModule::init()
 
     if (config().has("PYTHON_PRELOAD")) preloadModules();
     do_load_py_register();
+
+    PyGILState_Release(gstate);
 }
 
 bool PythonModule::preloadModules()
@@ -156,7 +168,8 @@ bool PythonModule::preloadModules()
     return true;
 }
 
-/// do_load_py -- load python code, given a file name. (Implements the loadpy command)
+/// do_load_py -- load python code, given a file name. (Implements the
+/// loadpy command)
 ///
 /// It is expected that the file contains a python module. The module
 /// should implement either a mind-agent, or it should contain a 'request'
@@ -227,7 +240,8 @@ std::string PythonModule::do_load_py(Request *dummy, std::list<std::string> args
             bool is_shell = thingsInModule.req_is_shell[i];
 
             // CogServer commands in Python
-            // Register request with cogserver using dotted name: module.RequestName
+            // Register request with cogserver using dotted name:
+            // module.RequestName
             std::string dottedName = moduleName + "." + s;
             // register the agent with a custom factory that knows how to
             PythonRequestFactory* fact =