Fix python3 warnings and errors in v.surf.icw (#355)

* fix python3 warnings
* futurize
* remove auto added python3

grass7/vector/v.surf.icw/v.surf.icw.py

@@ -120,6 +120,9 @@
 #% description: Number of parallel processes to launch
 #%end
 
+from __future__ import unicode_literals
+from builtins import str
+from builtins import range
 import sys
 import os
 import atexit
@@ -148,7 +151,7 @@ def main():
     where = options['where']
     workers = int(options['workers'])
 
-    if workers is 1 and "WORKERS" in os.environ:
+    if workers == 1 and "WORKERS" in os.environ:
         workers = int(os.environ["WORKERS"])
     if workers < 1:
         workers = 1
@@ -214,7 +217,7 @@ def main():
 
     # Needed to strip away empty entries from MS Windows newlines
     #   list() is needed for Python 3 compatibility
-    points_list = list(filter(None, points_list))
+    points_list = list([_f for _f in points_list if _f])
 
     # convert into a 2D list, drop unneeded cat column
     # to drop cat col, add this to the end of the line [:-1]
@@ -284,14 +287,14 @@ def main():
                                         start_coordinates = easting + ',' + northing,
                                         quiet = True)
         # stall to wait for the nth worker to complete,
-        if num % workers is 0:
+        if num % workers == 0:
             proc[num-1].wait()
 
         num += 1
 
     # make sure everyone is finished
     for i in range(n):
-        if proc[i].wait() is not 0:
+        if proc[i].wait() != 0:
             grass.fatal(_('Problem running %s') % 'r.cost')
 
 
@@ -310,13 +313,13 @@ def main():
                       cost_n_cleansed = cost_site_name + '.cleansed',
                       cost_n = cost_site_name, quiet = True)
         # stall to wait for the nth worker to complete,
-        if (i+1) % workers is 0:
+        if (i+1) % workers == 0:
             #print 'stalling ...'
             proc[i].wait()
 
     # make sure everyone is finished
     for i in range(n):
-        if proc[i].wait() is not 0:
+        if proc[i].wait() != 0:
             grass.fatal(_('Problem running %s') % 'r.mapcalc')
 
 
@@ -352,7 +355,7 @@ def main():
                                       friction = friction,
                                       quiet = True)
         # stall to wait for the nth worker to complete,
-        if (i+1) % workers is 0:
+        if (i+1) % workers == 0:
             #print 'stalling ...'
             proc[i].wait()
 
@@ -361,7 +364,7 @@ def main():
 
     # make sure everyone is finished
     for i in range(n):
-        if proc[i].wait() is not 0:
+        if proc[i].wait() != 0:
             grass.fatal(_('Problem running %s') % 'r.mapcalc')
 
     grass.run_command('g.remove', flags = 'f', type = 'raster',
@@ -453,7 +456,7 @@ def main():
                       quiet = True)
 
         # stall to wait for the nth worker to complete,
-        if num % workers is 0:
+        if num % workers == 0:
             proc[num-1].wait()
 
         # free up disk space ASAP