RF: Remove check for multiprocessing; its in standard library

The multiprocessing package was moved to standard library in
Python 2.7, and we have already dropped Python 2.6 support.

fissa/core.py

@@ -10,6 +10,7 @@
 
 import collections
 import glob
+from multiprocessing import Pool
 import os.path
 import sys
 import warnings
@@ -22,15 +23,6 @@
 from . import neuropil as npil
 from . import roitools
 
-try:
-    from multiprocessing import Pool
-    has_multiprocessing = True
-except ImportError:
-    warnings.warn('Multiprocessing library is not installed, using single ' +
-                  'core instead. To use multiprocessing install it by: ' +
-                  'pip install multiprocessing')
-    has_multiprocessing = False
-
 
 def extract_func(inputs):
     """Extract data using multiprocessing.
@@ -306,7 +298,6 @@ def separation_prep(self, redo=False):
 
             # Check whether we should use multiprocessing
             use_multiprocessing = (
-                has_multiprocessing and
                 (self.ncores_preparation is None or self.ncores_preparation > 1)
             )
             # Do the extraction
@@ -437,7 +428,6 @@ def separate(self, redo_prep=False, redo_sep=False):
 
             # Check whether we should use multiprocessing
             use_multiprocessing = (
-                has_multiprocessing and
                 (self.ncores_separation is None or self.ncores_separation > 1)
             )
             # Do the extraction