Avoid pip version check.

.travis.yml

@@ -43,8 +43,8 @@ matrix:
       stage: lint
 
 install:
-    - pip install -U pip setuptools wheel | cat
-    - pip install -U tox | cat
+    - pip --disable-pip-version-check install -U pip setuptools wheel | cat
+    - pip --disable-pip-version-check install -U tox | cat
 script: tox -v -- -v
 after_success:
   - .tox/$TRAVIS_PYTHON_VERSION/bin/coverage xml

tox.ini

@@ -36,6 +36,8 @@ basepython =
     3.7: python3.7
     pypy,pypy3: pypy
 
+install_command = python -m pip --disable-pip-version-check install {opts} {packages}
+
 [testenv:apicheck]
 commands = pip install -U -r{toxinidir}/requirements/dev.txt
     sphinx-build -j2 -b apicheck -d {envtmpdir}/doctrees docs docs/_build/apicheck