Addresses Issue pypa#5572: Implement PIP_TRUSTED_HOSTS logic...

Duplicated logic around line 204 in core.py to allow users to specify
index via --index command-line option and validate against
PIP_TRUSTED_HOSTS when determining verify_ssl value.

pipenv/core.py

@@ -2366,8 +2366,21 @@ def do_install(
  )
  # Add the package to the Pipfile.
  if index_url:
+ trusted_hosts = get_trusted_hosts()
+ host_and_port = get_host_and_port(index_url)
+ require_valid_https = not any(
+ (
+ v in trusted_hosts
+ for v in (
+ host_and_port,
+ host_and_port.partition(":")[
+ 0
+ ], # also check if hostname without port is in trusted_hosts
+ )
+ )
+ )
  index_name = project.add_index_to_pipfile(
- index_url, verify_ssl=index_url.startswith("https:")
+ index_url, verify_ssl=require_valid_https
  )
  pkg_requirement.index = index_name
  try: