hgweb.cgi

hgweb: do not import uuid immediately to avoid its side effect

With hgdemandimport disabled (chg's case), `import uuid` has an immediate
side effect calling `ctypes.util.find_library` trying to locate the
`libuuid` library.  This happens at `import` time before `dispatch.run()`.
The call trace is like:

  File "hg/hg", line 54, in <module>
    from mercurial import (
  File "hg/mercurial/dispatch.py", line 24, in <module>
    from . import (
  File "hg/mercurial/commands.py", line 23, in <module>
    from . import (
  File "hg/mercurial/help.py", line 33, in <module>
    from .hgweb import (
  File "hg/mercurial/hgweb/__init__.py", line 20, in <module>
    from . import (
  File "hg/mercurial/hgweb/hgweb_mod.py", line 14, in <module>
    from .common import (
  File "hg/mercurial/hgweb/common.py", line 15, in <module>
    import uuid
  File "/usr/lib64/python2.7/uuid.py", line 404, in <module>
    lib = ctypes.CDLL(ctypes.util.find_library(libname))

The problem is, `ctypes.util.find_library` will execute
`sh -c '/sbin/ldconfig -p 2>/dev/null'` on Python <= 2.7.12. The output of
`sh` may pollute the terminal:

  shell-init: error retrieving current directory: getcwd: cannot access
  parent directories: No such file or directory

This patch moves `import uuid` so its side-effect can only happen after the
cwd check in `dispatch._getlocal`. Therefore the terminal won't be
polluted by importing `uuid`.

Differential Revision: https://phab.mercurial-scm.org/D1024

#!/usr/bin/env python
#
# An example hgweb CGI script, edit as necessary
# See also https://mercurial-scm.org/wiki/PublishingRepositories

# Path to repo or hgweb config to serve (see 'hg help hgweb')
config = "/path/to/repo/or/config"

# Uncomment and adjust if Mercurial is not installed system-wide
# (consult "installed modules" path from 'hg debuginstall'):
#import sys; sys.path.insert(0, "/path/to/python/lib")

# Uncomment to send python tracebacks to the browser if an error occurs:
#import cgitb; cgitb.enable()

from mercurial import demandimport; demandimport.enable()
from mercurial.hgweb import hgweb, wsgicgi
application = hgweb(config)
wsgicgi.launch(application)