Travis builds: always build manylinux wheels

This also reformats the YAML, for which I apologize, but it was hard to
work on it without doing that.

It drops dist: xenial which has become the default.

It renames matrix: to jobs: because that's the preferres spelling
according to Travis CI docs.

It adds names to all the special build jobs.

It moves regular Linux Python builds outside build matrix, for
conciseness (unfortunately this means 3.6 builds are now done twice:
once without -fwrapv and once with)

It moves docker pull and twine upload out of .manylinux.sh and into
.travis.yml.

It unifies twine upload calls by supplifying username/password via
environment variables.

The changes largely mirror those in
https://github.com/zopefoundation/BTrees/pull/115.

.manylinux.sh

@@ -2,8 +2,4 @@
 
 set -e -x
 
-docker pull $DOCKER_IMAGE
-
-docker run --rm -v `pwd`:/io $DOCKER_IMAGE $PRE_CMD /io/.manylinux-install.sh
-
-pip install twine && twine upload -u zope.wheelbuilder -p $PYPIPASSWORD wheelhouse/*
+docker run --rm -v "$(pwd)":/io $DOCKER_IMAGE $PRE_CMD /io/.manylinux-install.sh

.travis.yml

 language: python
-dist: xenial
-matrix:
-    include:
-        - os: linux
-          python: 2.7
-        - name: 2.7-pure
-          os: linux
-          python: 2.7
-          env: PURE_PYTHON=1
-        - os: linux
-          python: 3.5
-        - os: linux
-          python: 3.6
-          # Test for https://github.com/zopefoundation/persistent/issues/86
-          env: CFLAGS="-fno-wrapv"
-        - os: linux
-          python: pypy
-        - os: linux
-          python: pypy3
-        - os: linux
-          python: 3.7
-        - name: 3.7-pure
-          os: linux
-          python: 3.7
-          env: PURE_PYTHON=1
-        - os: linux
-          python: 3.8
-        - name: docs
-          os: linux
-          python: 3.6
-          install:
-            - pip install -U -e .[docs]
-          script:
-            - sphinx-build -b html -d docs/_build/doctrees docs docs/_build/html
-            - sphinx-build -b doctest -d docs/_build/doctrees docs docs/_build/doctest
-          after_success:
-        # It's important to use 'macpython' builds to get the least
-        # restrictive wheel tag. It's also important to avoid
-        # 'homebrew 3' because it floats instead of being a specific version.
-        - os: osx
-          language: generic
-          env: TERRYFY_PYTHON='macpython 2.7'
-        - os: osx
-          language: generic
-          env: TERRYFY_PYTHON='macpython 3.5'
-        - os: osx
-          language: generic
-          env: TERRYFY_PYTHON='macpython 3.6.0'
-        - os: osx
-          language: generic
-          env: TERRYFY_PYTHON='macpython 3.7.0'
-        - services:
-            - docker
-          env: DOCKER_IMAGE=quay.io/pypa/manylinux1_x86_64
-          before_install:
-            - if [[ $TRAVIS_TAG ]]; then bash .manylinux.sh; fi
-            - exit 0
-        - services:
-            - docker
-          env:
-            - DOCKER_IMAGE=quay.io/pypa/manylinux1_i686
-            - PRE_CMD=linux32
-          before_install:
-            - if [[ $TRAVIS_TAG ]]; then bash .manylinux.sh; fi
-            - exit 0
+
+env:
+  global:
+    - TWINE_USERNAME: zope.wheelbuilder
+    # this sets $PYPIPASSWORD
+    - secure: "NTWzDr5p8KRPNt+sniTot7csbzC87rzir/XfLtENE0GpQ49FlKw3lBhsDqAPoD8Ea5lwiHXmC/C/ci1UZhFvVEkAoQ2qJlMRnhqUdRJSrqcitmRt0fT6mLaTd+Lr+DxKlBxpssobrEm2G42V/G1s0Ggym04OqF8T+s6MF5ywgJM="
+
+python:
+  - 2.7
+  - 3.5
+  - 3.6
+  - 3.7
+  - 3.8
+  - pypy
+  - pypy3
+
+jobs:
+  include:
+
+    # Special Linux builds
+    - name: "Python: 2.7, pure (no C extensions)"
+      python: 2.7
+      env: PURE_PYTHON=1
+
+    # Test for https://github.com/zopefoundation/persistent/issues/86
+    - name: "Python: 3.6, -fno-wrapv"
+      python: 3.6
+      env: CFLAGS="-fno-wrapv"
+
+    - name: "Python: 3.7, pure (no C extensions)"
+      python: 3.7
+      env: PURE_PYTHON=1
+
+    - name: "Documentation"
+      python: 3.6
+      install:
+        - pip install -U -e .[docs]
+      script:
+        - sphinx-build -b html -d docs/_build/doctrees docs docs/_build/html
+        - sphinx-build -b doctest -d docs/_build/doctrees docs docs/_build/doctest
+      after_success:
+
+    # manylinux wheel builds
+    - name: 64-bit manylinux wheels (all Pythons)
+      services: docker
+      env: DOCKER_IMAGE=quay.io/pypa/manylinux1_x86_64
+      install: docker pull $DOCKER_IMAGE
+      script: bash .manylinux.sh
+
+    - name: 32-bit manylinux wheels (all Pythons)
+      services: docker
+      env: DOCKER_IMAGE=quay.io/pypa/manylinux1_i686 PRE_CMD=linux32
+      install: docker pull $DOCKER_IMAGE
+      script: bash .manylinux.sh
+
+    # It's important to use 'macpython' builds to get the least
+    # restrictive wheel tag. It's also important to avoid
+    # 'homebrew 3' because it floats instead of being a specific version.
+    - name: Python 2.7 wheels for MacOS
+      os: osx
+      language: generic
+      env: TERRYFY_PYTHON='macpython 2.7'
+    - name: Python 3.5 wheels for MacOS
+      os: osx
+      language: generic
+      env: TERRYFY_PYTHON='macpython 3.5'
+    - name: Python 3.6 wheels for MacOS
+      os: osx
+      language: generic
+      env: TERRYFY_PYTHON='macpython 3.6.0'
+    - name: Python 3.7 wheels for MacOS
+      os: osx
+      language: generic
+      env: TERRYFY_PYTHON='macpython 3.7.0'
 
 before_install:
-    - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then git clone https://github.com/MacPython/terryfy; fi
-    - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then source terryfy/travis_tools.sh; fi
-    - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then get_python_environment $TERRYFY_PYTHON venv; fi
-    - pip install -U pip setuptools cffi wheel coverage coveralls
+  - |
+    if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
+      git clone https://github.com/MacPython/terryfy
+      source terryfy/travis_tools.sh
+      get_python_environment $TERRYFY_PYTHON venv
+    fi
+
 install:
-    - pip install -U -e .[test]
+  - pip install -U pip setuptools cffi wheel coverage coveralls
+  - pip install -U -e .[test]
+
 script:
-    - python --version
-    # make sure we can build a wheel
-    - python setup.py bdist_wheel
-    # coverage makes PyPy run about 3x slower, but the tests only take
-    # .4s to begin with (the whole process takes about 1.5), so that's
-    # still only 4.5s, which is maneagable.
-    - coverage run -m zope.testrunner --test-path=. --auto-color --auto-progress
-notifications:
-    email: false
+  - python --version
+
+  # make sure we can build a wheel
+  - python setup.py bdist_wheel
+
+  # coverage makes PyPy run about 3x slower, but the tests only take
+  # .4s to begin with (the whole process takes about 1.5), so that's
+  # still only 4.5s, which is maneagable.
+  - coverage run -m zope.testrunner --test-path=. --auto-color --auto-progress
+
 after_success:
-    - coveralls
-    - echo [distutils]                                  > ~/.pypirc
-    - echo index-servers = pypi                        >> ~/.pypirc
-    - echo [pypi]                                      >> ~/.pypirc
-    - echo username=zope.wheelbuilder                  >> ~/.pypirc
-    - echo password=$PYPIPASSWORD                      >> ~/.pypirc
-    - if [[ $TRAVIS_TAG && "$TRAVIS_OS_NAME" == "osx" ]]; then pip install twine; fi
-    - if [[ $TRAVIS_TAG && "$TRAVIS_OS_NAME" == "osx" ]]; then python setup.py bdist_wheel; fi
-    - if [[ $TRAVIS_TAG && "$TRAVIS_OS_NAME" == "osx" ]]; then twine upload dist/*; fi
+  - coveralls
+  - |
+    if [[ $TRAVIS_TAG && "$TRAVIS_OS_NAME" == "osx" ]]; then
+      pip install twine
+      python setup.py bdist_wheel
+      TWINE_PASSWORD=$PYPIPASSWORD twine upload --skip-existing dist/*
+    fi
+  - |
+    if [[ $TRAVIS_TAG && -n "$DOCKER_IMAGE" ]]; then
+      pip install twine
+      TWINE_PASSWORD=$PYPIPASSWORD twine upload --skip-existing wheelhouse/*
+    fi
 
-env:
-    global:
-        secure: "NTWzDr5p8KRPNt+sniTot7csbzC87rzir/XfLtENE0GpQ49FlKw3lBhsDqAPoD8Ea5lwiHXmC/C/ci1UZhFvVEkAoQ2qJlMRnhqUdRJSrqcitmRt0fT6mLaTd+Lr+DxKlBxpssobrEm2G42V/G1s0Ggym04OqF8T+s6MF5ywgJM="
+notifications:
+  email: false
+
+cache: pip