fix testpypi install

Author: chaimleib

CHANGELOG.md

@@ -5,8 +5,10 @@
     - Travis testing for 3.7 (needed OpenSSL, sudo and Xenial)
 - Fixed:
     - PyPI wasn't rendering markdown because I didn't tell it what format to use.
+    - Python 2 wasn't installing via pip because of a new utils package. It has been zapped.
+- Maintainers:
     - TestPyPI version strings count from the latest tagged commit, which should be the last release
-    - Fix for Python 2 by removing utils package
+    - Install from TestPyPI works via `make install-testpypi`
 
 ## Version 3.0.0
 - Breaking:

Makefile

@@ -65,7 +65,10 @@ clean-temps:
 	rm -rf $(TEMPS)
 
 install-testpypi:
-	pip install --index-url https://test.pypi.org/simple/ intervaltree
+	pip install \
+		--index-url https://test.pypi.org/simple/ \
+		--extra-index-url https://pypi.org/simple \
+		intervaltree
 
 install-pypi:
 	pip install intervaltree