First commands with basic structure.

- Moves DBManager to common.

watchtower-plugin/exceptions.py

@@ -0,0 +1,37 @@
+class BasicException(Exception):
+    def __init__(self, msg, **kwargs):
+        self.msg = msg
+        self.kwargs = kwargs
+
+    def __str__(self):
+        if len(self.kwargs) > 2:
+            params = "".join("{}={}, ".format(k, v) for k, v in self.kwargs.items())
+
+            # Remove the extra 2 characters (space and comma) and add all data to the final message.
+            message = self.msg + " ({})".format(params[:-2])
+
+        else:
+            message = self.msg
+
+        return message
+
+    def to_json(self):
+        response = {"error": self.msg}
+        response.update(self.kwargs)
+        return response
+
+
+class InvalidParameter(BasicException):
+    """Raised when a command line parameter is invalid (either missing or wrong)"""
+
+
+class InvalidKey(BasicException):
+    """Raised when there is an error loading the keys"""
+
+
+class TowerConnectionError(BasicException):
+    """Raised when the tower responds with an error"""
+
+
+class TowerResponseError(BasicException):
+    """Raised when the tower responds with an error"""