replace exits with raises in grid_setup, and remove the realtime check

gridded_glm/libexec/_minute_gridder.py

@@ -206,34 +206,20 @@ def grid_setup(glm_files, args, work_dir=os.getcwd()):
     min_events = None
     min_groups = None
 
-    if args.realtime:
-        if len(args.filenames) != 1:
-            log.error("realtime mode only accepts one input file")
-            exit(1)
-        glminfo = parse_glm_filename(os.path.basename(args.filenames[0]))
+    if len(glm_files) != 3:
+        raise RuntimeError("expected three files for this minute, only received {}".format(len(glm_files)))
 
-        globstring = "{}_{}_{}_s{}*".format(glminfo[0], glminfo[1], glminfo[2], glminfo[3].strftime("%Y%j%H%M"))
-        fileglob = glob(os.path.join(os.path.dirname(args.filenames[0]), globstring))
-        if len(fileglob) != 3:
-            log.error("There are not (yet) three GLM files from this minute. This may be expected. Exiting.")
-            exit(0)
-        args.filenames = fileglob
-
-    for f in args.filenames:
+    for f in glm_files:
         if not os.path.exists(f):
-            log.error("Tried to grid file that does not exist: {}".format(f))
-            exit(1)
+            raise RuntimeError("Tried to grid file that does not exist: {}".format(f))
 
     if "meso" in args.goes_sector and (args.ctr_lat == None or args.ctr_lon == None):
-        log.error("sector 'meso' requires --ctr-lat & --ctr-lon")
-        exit(1)
+        raise RuntimeError("sector 'meso' requires --ctr-lat & --ctr-lon")
 
     try:
         start_time, end_time = get_start_end(glm_files)
     except:
-        log.error("Could not parse start & end times from one or more of the files provided:")
-        log.error(", ".join(glm_files))
-        exit(1)
+        raise RuntimeError("Could not parse start & end times from one or more of the files provided: {}".format(", ".join(glm_files)))
 
     base_date = datetime(start_time.year, start_time.month, start_time.day)
     proj_name = 'geos'