MAJOR: sort out config file parsing

If sections are left blank, commented out or just don't exist, the
defualts will be used.

The only potential bad thing about this change is that it no longer
checks and reports individual value errors, like suppling a string
to the 'verbosity' option.

archmap.py

@@ -320,6 +320,7 @@ def make_csv(parsed_users, output_file=''):
 def main():
     from argparse import ArgumentParser
     from configparser import ConfigParser
+    from pathlib import Path
 
     # Define and parse arguments.
     parser = ArgumentParser(description='ArchMap GeoJSON/KML generator')
@@ -346,28 +347,23 @@ def main():
                         help="Output the CSV to FILE, use 'no' to disable output or '-' to print to stdout")
     args = parser.parse_args()
 
+    config_location = Path(args.config)
+    config = ConfigParser()
+
     # Try to use the config file. If it doesn't exist, use the defaults.
-    try:
-        config = ConfigParser()
-        config.read(args.config)
-        verbosity = int(config['extras']['verbosity'])
-        pretty = config.getboolean('extras', 'pretty')
-        input_url = config['files']['url']
-        input_file = config['files']['file']
-        output_file_users = config['files']['users']
-        output_file_geojson = config['files']['geojson']
-        output_file_kml = config['files']['kml']
-        output_file_csv = config['files']['csv']
-    except Exception as e:
-        log.warning('Warning: Configuation file error: {}. Using defaults'.format(e))
-        verbosity = default_verbosity
-        pretty = default_pretty
-        input_url = default_url
-        input_file = default_file
-        output_file_users = default_users
-        output_file_geojson = default_geojson
-        output_file_kml = default_kml
-        output_file_csv = default_csv
+    if not config_location.is_file():
+        log.warning('Warning: Configuation file does not exist. Using defaults')
+    else:
+        config.read(str(config_location))
+
+    verbosity = config.getint('extras', 'verbosity', fallback=default_verbosity)
+    pretty = config.getboolean('extras', 'pretty', fallback=default_pretty)
+    input_url = config.get('files', 'url', fallback=default_url)
+    input_file = config.get('files', 'file', fallback=default_file)
+    output_file_users = config.get('files', 'users', fallback=default_users)
+    output_file_geojson = config.get('files', 'geojson', fallback=default_geojson)
+    output_file_kml = config.get('files', 'kml', fallback=default_kml)
+    output_file_csv = config.get('files', 'csv', fallback=default_csv)
 
     # Finally, parse the command line arguments, anything passed to them will
     # override both the defaults in this script and anything in the config file.