d.polar: fail fast if map does not exist

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@70462 15284696-431f-4ddb-bdfa-cd5b030d7da7

scripts/d.polar/d.polar.py

@@ -53,6 +53,11 @@ from grass.script.utils import try_remove, basename
 from grass.script import core as gcore
 
 
+def raster_map_required(name):
+    if not gcore.find_file(name, 'cell')['file']:
+        gcore.fatal(_("Raster map <%s> not found") % name)
+
+
 def cleanup():
     try_remove(tmp)
     for f in glob.glob(tmp + '_*'):
@@ -418,6 +423,8 @@ def main():
         gcore.fatal(
             _("xgraph required, please install first (www.xgraph.org)"))
 
+    raster_map_required(map)
+
     #################################
     # this file contains everything:
     rawfile = tmp + "_raw"