explicitly check for IPython version

liquid_tags/notebook.py

@@ -48,11 +48,12 @@ import re
 import os
 from .mdx_liquid_tags import LiquidTags
 
-try:
-    from IPython import nbconvert
-except ImportError:
+import IPython
+if IPython.__version__.split('.')[0] != 1:
     raise ValueError("IPython version 1.0+ required for notebook tag")
 
+from IPython import nbconvert
+
 from IPython.nbconvert.filters.highlight import _pygment_highlight
 from pygments.formatters import HtmlFormatter