Adjustment to FSLDirDialog behaviour. Also fixed default to /usr/local,

as it wasn't working previously.

fsl/utils/dialog.py

@@ -18,6 +18,7 @@ use throughout ``fslpy``. The available dialogs are:
 """
 
 
+import            os
 import os.path as op
 import            threading
 
@@ -709,11 +710,14 @@ class FSLDirDialog(wx.Dialog):
         dlg = wx.DirDialog(
             self,
             message='Select the directory in which FSL is installed',
-            defaultPath=op.join('usr', 'local'),
+            defaultPath=op.join(os.sep, 'usr', 'local'),
             style=wx.DD_DEFAULT_STYLE | wx.DD_DIR_MUST_EXIST)
 
+        # If the user cancels the file
+        # dialog, focus returns to the
+        # original 'Choose dir' / 'Skip'
+        # dialog.
         if dlg.ShowModal() != wx.ID_OK:
-            self.EndModal(wx.ID_CANCEL)
             return
 
         self.__fsldir = dlg.GetPath()