Many linux builders' virtualenv are busted

[jdm]

servo/servo#21220 included a change the the WPT requirements.txt which yields:

"/home/servo/buildbot/slave/linux-dev/build/python/_virtualenv/bin/python2.7" "-m" "pip" "install" "-I" "-r" "/home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt" failed with error code -11:
Output:
Collecting html5lib==1.0.1 (from -r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 1))
  Using cached https://files.pythonhosted.org/packages/a5/62/bbd2be0e7943ec8504b517e62bab011b4946e1258842bc159e5dfde15b96/html5lib-1.0.1-py2.py3-none-any.whl
Collecting mozinfo==0.10 (from -r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 2))
Collecting mozlog==3.8 (from -r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 3))
  Using cached https://files.pythonhosted.org/packages/c7/ee/4bed8dc52829fdf8c3a00578530f2b36407567d7f2ec9accdc826ef1c887/mozlog-3.8-py2-none-any.whl
Collecting mozdebug==0.1 (from -r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 4))
Collecting urllib3[secure]==1.22 (from -r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
  Using cached https://files.pythonhosted.org/packages/63/cb/6965947c13a94236f6d4b8223e21beb4d576dc72e8130bd7880f600839b8/urllib3-1.22-py2.py3-none-any.whl
Collecting six>=1.9 (from html5lib==1.0.1->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 1))
  Using cached https://files.pythonhosted.org/packages/67/4b/141a581104b1f6397bfa78ac9d43d8ad29a7ca43ea90a2d863fe3056e86a/six-1.11.0-py2.py3-none-any.whl
Collecting webencodings (from html5lib==1.0.1->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 1))
  Using cached https://files.pythonhosted.org/packages/f4/24/2a3e3df732393fed8b3ebf2ec078f05546de641fe1b667ee316ec1dcf3b7/webencodings-0.5.1-py2.py3-none-any.whl
Collecting mozfile>=0.12 (from mozinfo==0.10->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 2))
Collecting mozterm (from mozlog==3.8->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 3))
  Using cached https://files.pythonhosted.org/packages/ab/eb/0c53684f5821d666372c6ea03d8c64558c8f74fda0fd5b24ae3dd2ab6a95/mozterm-1.0.0-py2.py3-none-any.whl
Collecting blessings>=1.3 (from mozlog==3.8->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 3))
  Using cached https://files.pythonhosted.org/packages/8d/b1/a3fe6fd8a012e6d019bafd671c2fee0597ea97ff2e76c25aadfa4545fc32/blessings-1.7-py2-none-any.whl
Collecting idna>=2.0.0; python_version <= "2.7" and extra == "secure" (from urllib3[secure]==1.22->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
  Using cached https://files.pythonhosted.org/packages/4b/2a/0276479a4b3caeb8a8c1af2f8e4355746a97fab05a372e4a2c6a6b876165/idna-2.7-py2.py3-none-any.whl
Collecting pyOpenSSL>=0.14; python_version <= "2.7" and extra == "secure" (from urllib3[secure]==1.22->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
  Using cached https://files.pythonhosted.org/packages/96/af/9d29e6bd40823061aea2e0574ccb2fcf72bfd6130ce53d32773ec375458c/pyOpenSSL-18.0.0-py2.py3-none-any.whl
Collecting cryptography>=1.3.4; python_version <= "2.7" and extra == "secure" (from urllib3[secure]==1.22->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
  Using cached https://files.pythonhosted.org/packages/67/21/e79987f1f9abae42d666b1f89b4e78aa096acc00bbf97ad40d19b07b4a83/cryptography-2.3-cp27-cp27mu-manylinux1_x86_64.whl
Collecting certifi; extra == "secure" (from urllib3[secure]==1.22->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
  Using cached https://files.pythonhosted.org/packages/7c/e6/92ad559b7192d846975fc916b65f667c7b8c3a32bea7372340bfe9a15fa5/certifi-2018.4.16-py2.py3-none-any.whl
Collecting ipaddress; python_version <= "2.7" and extra == "secure" (from urllib3[secure]==1.22->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
  Using cached https://files.pythonhosted.org/packages/fc/d0/7fc3a811e011d4b388be48a0e381db8d990042df54aa4ef4599a31d39853/ipaddress-1.0.22-py2.py3-none-any.whl
Collecting enum34; python_version < "3" (from cryptography>=1.3.4; python_version <= "2.7" and extra == "secure"->urllib3[secure]==1.22->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
  Using cached https://files.pythonhosted.org/packages/c5/db/e56e6b4bbac7c4a06de1c50de6fe1ef3810018ae11732a50f15f62c7d050/enum34-1.1.6-py2-none-any.whl
Collecting cffi!=1.11.3,>=1.7 (from cryptography>=1.3.4; python_version <= "2.7" and extra == "secure"->urllib3[secure]==1.22->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
  Using cached https://files.pythonhosted.org/packages/14/dd/3e7a1e1280e7d767bd3fa15791759c91ec19058ebe31217fe66f3e9a8c49/cffi-1.11.5-cp27-cp27mu-manylinux1_x86_64.whl
Collecting asn1crypto>=0.21.0 (from cryptography>=1.3.4; python_version <= "2.7" and extra == "secure"->urllib3[secure]==1.22->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
  Using cached https://files.pythonhosted.org/packages/ea/cd/35485615f45f30a510576f1a56d1e0a7ad7bd8ab5ed7cdc600ef7cd06222/asn1crypto-0.24.0-py2.py3-none-any.whl
Collecting pycparser (from cffi!=1.11.3,>=1.7->cryptography>=1.3.4; python_version <= "2.7" and extra == "secure"->urllib3[secure]==1.22->-r /home/servo/buildbot/slave/linux-dev/build/tests/wpt/web-platform-tests/tools/wptrunner/requirements.txt (line 5))
Installing collected packages: six, webencodings, html5lib, mozfile, mozinfo, mozterm, blessings, mozlog, mozdebug, idna, enum34, pycparser, cffi, asn1crypto, ipaddress, cryptography, pyOpenSSL, certifi, urllib3
Successfully installed asn1crypto-0.24.0 blessings-1.7 certifi-2018.4.16 cffi-1.11.5 cryptography-2.3 enum34-1.1.6 html5lib-1.0.1 idna-2.7 ipaddress-1.0.22 mozdebug-0.1 mozfile-1.2 mozinfo-0.10 mozlog-3.8 mozterm-1.0.0 pyOpenSSL-18.0.0 pycparser-2.18 six-1.11.0 urllib3-1.23 webencodings-0.5.1
Error:
/home/servo/buildbot/slave/linux-dev/build/python/_virtualenv/local/lib/python2.7/site-packages/cryptography/hazmat/primitives/constant_time.py:26: CryptographyDeprecationWarning: Support for your Python version is deprecated. The next version of cryptography will remove support. Please upgrade to a 2.7.x release that supports hmac.compare_digest as soon as possible.
  utils.DeprecatedIn23,
awscli 1.15.56 has requirement botocore==1.10.55, but you'll have botocore 1.5.95 which is incompatible.
program finished with exit code 1
elapsedTime=2.219284

any time mach is invoked. The PR did not merge, but now subsequent PRs are showing the same problem.