Revised pandoc version detection.

IPython/nbconvert/utils/pandoc.py

@@ -15,6 +15,7 b' from __future__ import print_function'
 # Stdlib imports
 import subprocess
 import warnings
+import re
 from io import TextIOWrapper, BytesIO
 
 # IPython imports
@@ -89,8 +90,11 b' def get_pandoc_version():'
         out = subprocess.check_output(['pandoc', '-v'],
                                       universal_newlines=True)
         out_lines = out.splitlines()
-        pandoc_line = out_lines[0]
-        __version = pandoc_line.lstrip("pandoc ")
+        version_pattern = re.compile(r"^\d+(\.\d+){1,}$")
+        for tok in out_lines[0].split():
+            if version_pattern.match(tok):
+                __version = tok
+                break
     return __version
 
 
@@ -103,6 +107,12 b' def check_pandoc_version():'
       If pandoc is unavailable.
     """
     v = get_pandoc_version()
+    if v is None:
+        warnings.warn("Sorry, we cannot determine the version of pandoc.\n"
+                      "Please consider reporting this issue and include the"
+                      "output of pandoc --version.\nContinuing...",
+                      RuntimeWarning, stacklevel=2)
+    return False
     ok = check_version(v , _minimal_version )
     if not ok:
         warnings.warn( "You are using an old version of pandoc (%s)\n" % v +