Don't hard-code yelpcorp PyPI registry

This is controlled via the /etc/pip.conf file which is managed by Puppet
on yelpcorp hosts.

Makefile

@@ -11,7 +11,7 @@ endif
 
 NOOP = true
 ifeq ($(PAASTA_ENV),YELP)
-	export PIP_INDEX_URL ?= https://pypi.yelpcorp.com/simple
+	export PIP_INDEX_URL ?= $(shell pip3 config get --global global.index-url)
 	export NPM_CONFIG_REGISTRY ?= https://npm.yelpcorp.com/
 	ADD_MISSING_DEPS_MAYBE:=-diff --unchanged-line-format= --old-line-format= --new-line-format='%L' ./requirements.txt ./yelp_package/extra_requirements_yelp.txt >> ./requirements.txt
 else
@@ -87,7 +87,7 @@ example_cluster:
 	tox -e example-cluster
 
 yelpy:
-	.tox/py36/bin/pip-custom-platform install -i https://pypi.yelpcorp.com/simple -r yelp_package/extra_requirements_yelp.txt
+	.tox/py36/bin/pip install -r yelp_package/extra_requirements_yelp.txt
 
 LAST_COMMIT_MSG = $(shell git log -1 --pretty=%B | sed -e 's/[\x27\x22]/\\\x27/g')
 release:

debian/rules

@@ -20,10 +20,8 @@ override_dh_virtualenv:
 	dh_virtualenv --index-url $(PIP_INDEX_URL) \
                 --python=/usr/bin/python3.6 \
                 --preinstall cython==0.29.36 \
-                --preinstall pip-custom-platform \
                 --preinstall pip==9.0.1 \
-                --preinstall setuptools==46.1.3 \
-                --pip-tool pip-custom-platform \
+                --preinstall setuptools==46.1.3
 
 override_dh_installinit:
 	dh_installinit --noscripts

tox.ini

@@ -1,6 +1,5 @@
 [tox]
 envlist = py36
-tox_pip_extensions_ext_pip_custom_platform = true
 tox_pip_extensions_ext_venv_update = true
 
 [testenv]
@@ -9,7 +8,7 @@ deps =
     --requirement={toxinidir}/requirements.txt
     --requirement={toxinidir}/requirements-dev.txt
 usedevelop = true
-passenv = USER PIP_INDEX_URL
+passenv = USER
 setenv =
     YARN_REGISTRY = {env:NPM_CONFIG_REGISTRY:https://registry.npmjs.org/}
 whitelist_externals=
@@ -27,7 +26,7 @@ commands =
     check-requirements
     # optionally install yelpy requirements - this is after check-requirements since
     # check-requirements doesn't understand these extra requirements
-    -pip install --index-url https://pypi.yelpcorp.com/simple -r yelp_package/extra_requirements_yelp.txt
+    -pip install -r yelp_package/extra_requirements_yelp.txt
     # we then run tests at the very end so that we can run tests with yelpy requirements
     py.test -s {posargs:tests}