use pip on travis to ensure correct python version runtime

.travis.yml

@@ -15,8 +15,7 @@ env:
 
 install:
   - pip install -U pip --no-cache-dir
-  - pip install -U pipenv --no-cache-dir
-  - pipenv install --dev --skip-lock
+  - pip install -r development.txt
 
 script:
   - make $TEST_TYPE

Makefile

@@ -64,6 +64,7 @@ docs:
 
 prepare:
 	@reset
+	pip install -r development.txt
 
 
 .PHONY: docs lint pypi prepare clean pyopenssl unit functional test dependencies all

Pipfile

@@ -7,27 +7,27 @@ name = "pypi"
 six = "*"
 
 [dev-packages]
-ndg-httpsclient = "*"
 "flake8" = "*"
 "httplib2" = "*"
+"pathlib2" = "*"
+"urllib3" = "*"
+coverage = "*"
+cryptography = "==2.3"
 ipdb = "*"
 mock = "*"
+ndg-httpsclient = "*"
 nose = "*"
 nose-randomly = "*"
+pyopenssl = ">=17.5.0"
 rednose = "*"
 requests = {version = "*", extras = ["security"]}
-sure = "*"
-tornado = "*"
-coverage = "*"
+singledispatch = "*"
 sphinx = "*"
 sphinx-rtd-theme = "*"
-twine = "*"
-"pathlib2" = "*"
+sure = "*"
+tornado = "*"
 tox = "*"
-singledispatch = "*"
-pyopenssl = ">=17.5.0"
-cryptography = "==2.3"
-"urllib3" = "*"
+twine = "*"
 
 [requires]
 python_version = "3.6"