merge with crew

http: backout 181108726ea5, which breaks on Python 2.4

test-module-imports: try and detect virtualenv breakage (issue4129) virtualenvs (among other things) break the stdlib module detection in the import checker, and I don't see a good way to work around that for now.

http: reuse authentication info after the first failed request (issue3567) Context: mercurial access to repository server with http access, and this server is protected by basic auth. Before patch: * mercurial try an anonymous access to server, server return 401 response and mercurial resend request with login / password information After patch: * mercurial try an anonymous access to server, server return 401 response. For all subsequent requests, mercurial keep in memory this information (this server need basic auth information). This patch reduce the number of http access against mercurial server. Example, before patch : 10.10.168.170 - - [25/Oct/2013:15:44:51 +0200] "GET /hg/testagt?cmd=capabilities HTTP/1.1" 401 260 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:44:52 +0200] "GET /hg/testagt?cmd=capabilities HTTP/1.1" 200 147 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:00 +0200] "GET /hg/testagt?cmd=capabilities HTTP/1.1" 401 260 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:01 +0200] "GET /hg/testagt?cmd=capabilities HTTP/1.1" 200 147 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:03 +0200] "GET /hg/testagt?cmd=batch HTTP/1.1" 401 260 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:04 +0200] "GET /hg/testagt?cmd=batch HTTP/1.1" 200 42 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:06 +0200] "GET /hg/testagt?cmd=getbundle HTTP/1.1" 401 260 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:07 +0200] "GET /hg/testagt?cmd=getbundle HTTP/1.1" 200 61184 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:09 +0200] "GET /hg/testagt?cmd=listkeys HTTP/1.1" 401 260 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:10 +0200] "GET /hg/testagt?cmd=listkeys HTTP/1.1" 200 15 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:12 +0200] "GET /hg/testagt?cmd=listkeys HTTP/1.1" 401 260 "-" "mercurial/proto-1.0" 10.10.168.170 - - [25/Oct/2013:15:45:12 +0200] "GET /hg/testagt?cmd=listkeys HTTP/1.1" 200 - "-" "mercurial/proto-1.0" Example after patch : 10.10.168.170 - - [28/Oct/2013:11:49:14 +0100] "GET /hg/testagt?cmd=capabilities HTTP/1.1" 401 260 "-" "mercurial/proto-1.0" 10.10.168.170 - - [28/Oct/2013:11:49:15 +0100] "GET /hg/testagt?cmd=capabilities HTTP/1.1" 200 147 "-" "mercurial/proto-1.0" 10.10.168.170 - - [28/Oct/2013:11:49:17 +0100] "GET /hg/testagt?cmd=batch HTTP/1.1" 200 42 "-" "mercurial/proto-1.0" 10.10.168.170 - - [28/Oct/2013:11:49:19 +0100] "GET /hg/testagt?cmd=getbundle HTTP/1.1" 200 61184 "-" "mercurial/proto-1.0" 10.10.168.170 - - [28/Oct/2013:11:49:22 +0100] "GET /hg/testagt?cmd=listkeys HTTP/1.1" 200 15 "-" "mercurial/proto-1.0" 10.10.168.170 - - [28/Oct/2013:11:49:24 +0100] "GET /hg/testagt?cmd=listkeys HTTP/1.1" 200 - "-" "mercurial/proto-1.0" In this last example, you can see only one 401 response.