highlight: put pygments import inside demandimport.deactivated

I tripped on some weirdness relating to _thread vs threading way down
in a dep of highlight recently. I'm not really sure why I'm only just
seeing this defect now, but experimentally this fixes the problem, and
shouldn't cause any load-time slowness for people until pygments is
actually about to be used since highlight.highlight is still lazily
loaded in the highlight/__init__.py file.

hgext/highlight/highlight.py

@@ -1,88 +1,89 b''
 # highlight.py - highlight extension implementation file
 #
 #  Copyright 2007-2009 Adam Hupp <[e-mail]> and others
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 #
 # The original module was split in an interface and an implementation
 # file to defer pygments loading and speedup extension setup.
 
 from __future__ import absolute_import
 
-import pygments
-import pygments.formatters
-import pygments.lexers
-import pygments.util
-
 from mercurial import demandimport
 demandimport.ignore.extend(['pkgutil', 'pkg_resources', '__main__'])
 
 from mercurial import (
     encoding,
     util,
 )
 
+with demandimport.deactivated():
+    import pygments
+    import pygments.formatters
+    import pygments.lexers
+    import pygments.util
+
 highlight = pygments.highlight
 ClassNotFound = pygments.util.ClassNotFound
 guess_lexer = pygments.lexers.guess_lexer
 guess_lexer_for_filename = pygments.lexers.guess_lexer_for_filename
 TextLexer = pygments.lexers.TextLexer
 HtmlFormatter = pygments.formatters.HtmlFormatter
 
 SYNTAX_CSS = ('\n<link rel="stylesheet" href="{url}highlightcss" '
               'type="text/css" />')
 
 def pygmentize(field, fctx, style, tmpl, guessfilenameonly=False):
 
     # append a <link ...> to the syntax highlighting css
     old_header = tmpl.load('header')
     if SYNTAX_CSS not in old_header:
         new_header = old_header + SYNTAX_CSS
         tmpl.cache['header'] = new_header
 
     text = fctx.data()
     if util.binary(text):
         return
 
     # str.splitlines() != unicode.splitlines() because "reasons"
     for c in "\x0c\x1c\x1d\x1e":
         if c in text:
             text = text.replace(c, '')
 
     # Pygments is best used with Unicode strings:
     # <http://pygments.org/docs/unicode/>
     text = text.decode(encoding.encoding, 'replace')
 
     # To get multi-line strings right, we can't format line-by-line
     try:
         lexer = guess_lexer_for_filename(fctx.path(), text[:1024],
                                          stripnl=False)
     except (ClassNotFound, ValueError):
         # guess_lexer will return a lexer if *any* lexer matches. There is
         # no way to specify a minimum match score. This can give a high rate of
         # false positives on files with an unknown filename pattern.
         if guessfilenameonly:
             return
 
         try:
             lexer = guess_lexer(text[:1024], stripnl=False)
         except (ClassNotFound, ValueError):
             # Don't highlight unknown files
             return
 
     # Don't highlight text files
     if isinstance(lexer, TextLexer):
         return
 
     formatter = HtmlFormatter(nowrap=True, style=style)
 
     colorized = highlight(text, lexer, formatter)
     coloriter = (s.encode(encoding.encoding, 'replace')
                  for s in colorized.splitlines())
 
     tmpl.filters['colorize'] = lambda x: next(coloriter)
 
     oldl = tmpl.cache[field]
     newl = oldl.replace('line|escape', 'line|colorize')
     tmpl.cache[field] = newl