Exceptions

- Added `DanteException`
- Added `ProtocolException`
- Added `CommandException`

source/dante/exceptions.d

@@ -0,0 +1,43 @@
+module dante.exceptions;
+
+public abstract class DanteException : Exception
+{
+    this(string msg)
+    {
+        super(msg);
+    }
+}
+
+public class CommandException : DanteException
+{
+    this(string msg)
+    {
+        super(msg);
+    }
+}
+
+import std.conv : to;
+
+public class ProtocolException : DanteException
+{
+    this(string msg)
+    {
+        super(msg);
+    }
+
+    public static ProtocolException expectedMessageKind(TypeInfo_Class expected, Object got)
+    {
+        string message = "Expected message of type '"~to!(string)(expected);
+
+        if(got is null)
+        {
+            message ~= " but got null";
+        }
+        else
+        {
+            message ~= " but got a message of type '"~to!(string)(got.classinfo)~"'";
+        }
+
+        return new ProtocolException(message);
+    }
+}