Excel importConditions(): don't import formulas

In importCondtions() method, added the option "data_only=True" to the call to load_workbook(), so that the that values of a cell, and not the formulas, are imported into psychopy.

psychopy/data.py

@@ -2667,7 +2667,7 @@ def _assertValidVarNames(fieldNames, fileName):
             raise ImportError('openpyxl is required for loading excel '
                               'format files, but it was not found.')
         try:
-            wb = load_workbook(filename=fileName)
+            wb = load_workbook(filename=fileName, data_only=True)
         except Exception:  # InvalidFileException(unicode(e)): # this fails
             raise ImportError('Could not open %s as conditions' % fileName)
         ws = wb.worksheets[0]