webdriver exception puzzle

AccountSite.hs

{-# LANGUAGE OverloadedStrings, ScopedTypeVariables #-}
module AccountSite where

import Control.Monad.Trans (liftIO)
import Control.Exception (Exception, catch, throwIO)
import Control.Monad.Base (liftBase)
import qualified Data.Text as T
import Test.WebDriver (WDConfig(..), defaultConfig, chrome,
                       Capabilities(..), defaultCaps,
                       runSession,
                       openPage, findElem, Selector(..))
import Test.WebDriver.Commands.Wait (waitUntil)
import Test.WebDriver.Class (WebDriver)
import Test.WebDriver.Exceptions (FailedCommandType(NoSuchElement), FailedCommand(..))
import Text.Printf (printf, IsChar)

chromeConfig :: WDConfig
chromeConfig = defaultConfig { wdCapabilities = defaultCaps { browser = chrome }}

wait_time = 60.0

login :: WebDriver wd => String -> String -> wd ()
login home logged_in = do
  openPage home
  waitUntil wait_time (textAppears logged_in)
  return ()
  where
    textAppears txt = do
      (findElem (ByXPath expr) >> return ()) `catch` ignoreNoSuchElement
    -- ignoreNoSuchElement :: FailedCommandType -> wd ()
    -- ignoreNoSuchElement e = liftBase $ return ()
    ignoreNoSuchElement (FailedCommand NoSuchElement _) = return ()
    ignoreNoSuchElement e = liftBase (throwIO e)
    -- ignoreNoSuchElement step = catchJust isNoSuchElement (step >> return ()) ignore
    -- isNoSuchElement :: Exception e => e -> Maybe ()
    -- isNoSuchElement NoSuchElement = Just ()
    -- isNoSuchElement _ = Nothing
    -- ignore _ = return ()
    expr :: T.Text
    expr = T.pack $ printf "//div[contains(normalize-space(.), '%s')]" logged_in

txcollect.cabal

-- Initial txcollect.cabal generated by cabal init.  For further 
-- documentation, see http://haskell.org/cabal/users-guide/

name:                txcollect
version:             0.1.0.0
synopsis:            Collect Personal Finance Transactions
-- description:         
homepage:            http://www.madmode.com/
license:             MIT
license-file:        LICENSE
author:              Dan Connolly
maintainer:          [email protected]
-- copyright:           
category:            Web
build-type:          Simple
cabal-version:       >=1.8

-- executable txcollect
--   main-is: dm93.hs
--   other-modules: AccountSite
--  build-depends:       base ==4.6.*, webdriver, text, transformers-base

library
  exposed-modules:     AccountSite
  -- other-modules:       
  build-depends:       base ==4.6.*, webdriver, text, transformers-base

I'm losing thusly:

cabal configure && cabal build
Resolving dependencies...
Configuring txcollect-0.1.0.0...
Building txcollect-0.1.0.0...
Preprocessing library txcollect-0.1.0.0...
[1 of 1] Compiling AccountSite      ( AccountSite.hs, dist/build/AccountSite.o )

AccountSite.hs:25:24:
    Could not deduce (wd ~ IO)
    from the context (WebDriver wd)
      bound by the type signature for
                 login :: WebDriver wd => String -> String -> wd ()
      at AccountSite.hs:22:10-50
      `wd' is a rigid type variable bound by
           the type signature for
             login :: WebDriver wd => String -> String -> wd ()
           at AccountSite.hs:22:10
    Expected type: wd ()
      Actual type: IO ()
    In the return type of a call of `textAppears'
    In the second argument of `waitUntil', namely
      `(textAppears logged_in)'
    In a stmt of a 'do' block:
      waitUntil wait_time (textAppears logged_in)

Compilation exited abnormally with code 1 at Wed Sep  3 00:57:39