Included test for band parameter.

gts2_client/gts2_client.py

@@ -728,6 +728,9 @@ def client(outpath="", out_prefix="", out_mode="json", geo_ll=(), geo_ur=(), sen
     if out_mode == "stack" and "B01" in bands:
         raise AssertionError("Band 1 (B01) can not be stacked. Please request separately.")
 
+    if out_mode != "rgb" and bands == "":
+        raise AssertionError("Please provide at least one band.")
+
     valid_out_modes = ["json", "nc", "single", "stack", "python", "rgb"]
     try:
         assert out_mode in valid_out_modes
@@ -849,7 +852,7 @@ if __name__ == "__main__":
                         help="processing level (e.g. L2A)")
     parser.add_argument("-v", "--version", action="store", required=False, type=str, default="0.12",
                         help="version of atmospheric correction (e.g. 0.10)")
-    parser.add_argument("-b", "--bands", action="store", required=False, type=str,
+    parser.add_argument("-b", "--bands", action="store", required=False, type=str, default="",
                         help="list of Bands (e.g. -b B02_B03")
     parser.add_argument("-s", "--start_date", action="store", required=True, type=str,
                         help="Startdate e.g. 20160701")