Katropton: resolve a string bug with python3 in the get_gmsh_version function

katropton/utilities.py

@@ -20,7 +20,7 @@ from katropton.eigenvalues import *
 def get_gmsh_version():
     tmp = subprocess.check_output(["gmsh", "--version"],
                                   stderr=subprocess.STDOUT)
-    tmp2 = tmp.split('.')
+    tmp2 = tmp.decode().split('.')
     return int(tmp2[0]), int(tmp2[1]), int(tmp2[2])