r.vif: small fix python 2 left-over code (#594)

 r.vif: small fix python 2 left-over code

src/raster/r.vif/r.vif.py

@@ -98,7 +98,6 @@
     from cStringIO import StringIO
 import uuid
 import atexit
-import string
 import grass.script as gs
 
 
@@ -114,11 +113,15 @@ def cleanup():
         gs.run_command("g.remove", flags="f", type="all", name=rast, quiet=True)
 
 
+def create_unique_name(name):
+    """Generate a tmp name which contains prefix
+    Store the name in the global list.
+    """
+    return name + str(uuid.uuid4().hex)
+
+
 def tmpname(prefix):
-    """Generate a tmp name which contains prefix. Store the name in the
-    global list. Use only for raster maps."""
-    tmpf = prefix + str(uuid.uuid4())
-    tmpf = string.replace(tmpf, "-", "_")
+    tmpf = create_unique_name(prefix)
     CLEAN_RAST.append(tmpf)
     return tmpf