add MissingSubKeyError for config loading. update main.py for --config flag

src/pg_rad/main.py

@@ -1,8 +1,14 @@
 import argparse
+import logging
+import sys
 
-from pg_rad.logger import setup_logger
-from pg_rad.landscape import LandscapeDirector
-from pg_rad.plotting import LandscapeSlicePlotter
+from pandas.errors import ParserError
+from yaml import YAMLError
+
+from pg_rad.exceptions.exceptions import MissingNestedKeyError
+from pg_rad.logger.logger import setup_logger
+from pg_rad.landscape.director import LandscapeDirector
+from pg_rad.plotting.landscape_plotter import LandscapeSlicePlotter
 
 
 def main():
@@ -10,7 +16,10 @@ def main():
         prog="pg-rad",
         description="Primary Gamma RADiation landscape tool"
     )
-
+    parser.add_argument(
+        "--config",
+        help="Build from a config file."
+    )
     parser.add_argument(
         "--test",
         action="store_true",
@@ -29,12 +38,35 @@ def main():
 
     args = parser.parse_args()
     setup_logger(args.loglevel)
+    logger = logging.getLogger(__name__)
 
     if args.test:
         landscape = LandscapeDirector().build_test_landscape()
         plotter = LandscapeSlicePlotter()
         plotter.plot(landscape, save=args.saveplot)
 
+    elif args.config:
+        try:
+            landscape = LandscapeDirector.build_from_config(args.config)
+            plotter = LandscapeSlicePlotter()
+            plotter.plot(landscape, save=args.saveplot)
+        except (
+            MissingNestedKeyError,
+            KeyError,
+            YAMLError
+        ):
+            logger.critical(
+                "The provided config file is invalid. "
+                "Check the log above. You can consult the documentation for "
+                "an explanation of how to define a config file."
+                )
+            sys.exit(1)
+        except (
+            FileNotFoundError,
+            ParserError
+        ):
+            sys.exit(1)
+
 
 if __name__ == "__main__":
     main()