Start exception hierarchy; rename DBNotFound to DatabaseNotFound.

timesearch/__init__.py

@@ -423,10 +423,9 @@ def main(argv):
     args = parser.parse_args(argv)
     try:
         args.func(args)
-    except exceptions.DBNotFound as e:
-        message = '"%s" is not an existing database.'
+    except exceptions.DatabaseNotFound as e:
+        message = str(e)
         message += '\nHave you used any of the other utilities to collect data?'
-        message = message % e.path.absolute_path
         print(message)
         return 1
 

timesearch/exceptions.py

@@ -1,3 +1,19 @@
-class DBNotFound(FileNotFoundError):
-    def __init__(self, path):
-        self.path = path
+class TimesearchException(Exception):
+    '''
+    Base type for all of the Timesearch exceptions.
+    Subtypes should have a class attribute `error_message`. The error message
+    may contain {format} strings which will be formatted using the
+    Exception's constructor arguments.
+    '''
+    error_message = ''
+    def __init__(self, *args, **kwargs):
+        self.given_args = args
+        self.given_kwargs = kwargs
+        self.error_message = self.error_message.format(*args, **kwargs)
+        self.args = (self.error_message, args, kwargs)
+
+    def __str__(self):
+        return self.error_message
+
+class DatabaseNotFound(TimesearchException, FileNotFoundError):
+    error_message = 'Database file not found: "{}"'

timesearch/tsdb.py

@@ -124,7 +124,7 @@ class TSDB:
         self.filepath = pathclass.Path(filepath)
         if not self.filepath.is_file:
             if not do_create:
-                raise exceptions.DBNotFound(self.filepath)
+                raise exceptions.DatabaseNotFound(self.filepath)
             print('New database', self.filepath.relative_path)
 
         os.makedirs(self.filepath.parent.absolute_path, exist_ok=True)