FxCop not found when duplicate FxCop rules added

[dgrunwald]

SD-1918, originally created on 11/25/2012 12:45:41 by Matt Ward

If you add the same rules assembly to FxCop the error is hidden from the
user.

To reproduce:

1. Open a project in SharpDevelop. Open the Code Analysis tab in the
   project options.
2. Click the Add/Remove assembly rule button.
3. Add the FxCop rules folder to the list of directories

c:\program files (x86)\microsoft fxcop 10\rules\

4. Click OK.

Expected result:

Error message displayed to the user indicating that duplicate rules have
been added.

Actual result:

Error message indicates that FxCop cannot be found which is incorrect.
The actual error is logged to the SharpDevelop console window but not
shown anywhere in the user interface.