Split logic onto multiple lines.

IPython/nbconvert/filters/markdown.py

@@ -113,7 +113,10 b' def _verify_node(cmd):'
     except OSError:
          # Command not found
         return False
-    return return_code == 0 and check_version(out.lstrip('v'), '0.9.12')
+    if return_code:
+        # Command error
+        return False
+    return check_version(out.lstrip('v'), '0.9.12')
 
 # prefer md2html via marked if node.js >= 0.9.12 is available
 # node is called nodejs on debian, so try that first