Fix #1565: Show warning if Pygments throws an ErrorToken

CHANGES

@@ -12,6 +12,7 @@ Bugs fixed
 * #2243: Ignore strange docstring types for classes, do not crash
 * #2247: Fix #2205 breaks make html for definition list with classifiers
   that contains regular-expression like string
+* #1565: Show warning if Pygments throws an ErrorToken
 
 Release 1.3.4 (released Jan 12, 2016)
 =====================================

sphinx/highlighting.py

@@ -183,9 +183,13 @@ class PygmentsBridge(object):
         formatter = self.get_formatter(**kwargs)
         try:
             hlsource = highlight(source, lexer, formatter)
-        except ErrorToken:
+        except ErrorToken as exc:
             # this is most probably not the selected language,
             # so let it pass unhighlighted
+            if warn:
+                warn('Could not parse literal_block as "%s". highlighting skipped.' % lang)
+            else:
+                raise exc
             hlsource = highlight(source, lexers['none'], formatter)
         if self.dest == 'html':
             return hlsource

tests/root/markup.txt

@@ -266,6 +266,12 @@ Code blocks
        false
    end
 
+.. code-block:: c
+
+   import sys
+
+   sys.stdout.write('hello world!\n')
+
 
 Misc stuff
 ----------

tests/test_build_html.py

@@ -31,13 +31,14 @@ http://www.python.org/logo.png
 reading included file u'.*?wrongenc.inc' seems to be wrong, try giving an \
 :encoding: option\\n?
 %(root)s/includes.txt:4: WARNING: download file not readable: .*?nonexisting.png
-(%(root)s/markup.txt:351: WARNING: invalid single index entry u'')?
+(%(root)s/markup.txt:357: WARNING: invalid single index entry u'')?
 (%(root)s/undecodable.txt:3: WARNING: undecodable source characters, replacing \
 with "\\?": b?'here: >>>(\\\\|/)xbb<<<'
 )?"""
 
 HTML_WARNINGS = ENV_WARNINGS + """\
 %(root)s/images.txt:20: WARNING: no matching candidate for image URI u'foo.\\*'
+%(root)s/markup.txt:269: WARNING: Could not parse literal_block as "c". highlighting skipped.
 %(root)s/footnote.txt:60: WARNING: citation not found: missing
 %(root)s/markup.txt:158: WARNING: unknown option: &option
 """

tests/test_build_latex.py

@@ -27,6 +27,7 @@ LATEX_WARNINGS = ENV_WARNINGS + """\
 %(root)s/markup.txt:158: WARNING: unknown option: &option
 %(root)s/footnote.txt:60: WARNING: citation not found: missing
 %(root)s/images.txt:20: WARNING: no matching candidate for image URI u'foo.\\*'
+%(root)s/markup.txt:269: WARNING: Could not parse literal_block as "c". highlighting skipped.
 """
 
 if PY3: