DOC mention JOBLIB_START_METHOD in crash/freeze FAQ

Author: lesteve

doc/faq.rst

@@ -248,10 +248,13 @@ Python processes for parallel computing. Unfortunately this is a violation of
 the POSIX standard and therefore some software editors like Apple refuse to
 consider the lack of fork-safety in Accelerate / vecLib as a bug.
 
-In Python 3.4+ it is now possible to configure ``multiprocessing`` to use the
-'forkserver' or 'spawn' start methods (instead of the default 'fork') to manage
-the process pools. This makes it possible to not be subject to this issue
-anymore.
+In Python 3.4+ it is now possible to configure ``multiprocessing`` to
+use the 'forkserver' or 'spawn' start methods (instead of the default
+'fork') to manage the process pools. To work around this issue when
+using scikit-learn, you can set the JOBLIB_START_METHOD environment
+variable to 'forkserver'. However the user should be aware that using
+the 'forkserver' method prevents joblib.Parallel to call function
+interactively defined in a shell session.
 
 If you have custom code that uses ``multiprocessing`` directly instead of using
 it via joblib you can enable the 'forkserver' mode globally for your