Add PIP_NO_INPUT to environment passed variables passed to pip

[cryvate]

Currently, if the index-url requires a password prompt, but one of the extra-index-urls does not, virtualenv will fail, unless you set PIP_NO_INPUT=1 or similar. virtualenv requires pip to not ask for input, otherwise it will fail immediately, so we might as well tell pip so! Here:

env = {
    "PYTHONPATH": pythonpath,
    "JYTHONPATH": pythonpath,  # for Jython < 3.x
    "PIP_FIND_LINKS": findlinks,
    "PIP_USE_WHEEL": "1",
    "PIP_ONLY_BINARY": ":all:",
    "PIP_USER": "0",
}

Simply add another entry

    "PIP_NO_INPUT": "0",