Add testing under an sdist install

.travis.yml

@@ -1,26 +1,40 @@
+---
+
 language: python
 sudo: false
 cache:
   directories:
-  - "$HOME/.cache/pip"
+    - "$HOME/.cache/pip"
 python:
-- pypy
-- pypy3
-- '2.7'
-- '3.4'
-- '3.5'
-- '3.6'
+  - pypy
+  - pypy3
+  - '2.7'
+  - '3.4'
+  - '3.5'
+  - '3.6'
 matrix:
   fast_finish: true
   include:
-  - python: '3.7'
-    dist: xenial    # required for Python 3.7 (travis-ci/travis-ci#9069)
-    sudo: required  # required for Python 3.7 (travis-ci/travis-ci#9069)
+    - python: '3.7'
+      dist: xenial    # required for Python 3.7 (travis-ci/travis-ci#9069)
+      sudo: required  # required for Python 3.7 (travis-ci/travis-ci#9069)
+
+    # test under an sdist install
+    - python: 3.6
+      script:
+        - python setup.py sdist
+        # there are a bunch of ways of getting the version number... this is an
+        # easy one
+        #
+        # yamllint disable rule:line-length
+        - version="$(cat nose2/_version.py | grep '^__version__' |  cut -d "'" -f2)"
+        - (cd dist; tar -xzf "nose2-${version}.tar.gz")
+        - (cd "dist/nose2-${version}"; tox)
 install:
-- travis_retry pip install tox-travis
-- travis_retry pip install coveralls
-- travis_retry pip install coverage
+  - travis_retry pip install tox-travis
+  - travis_retry pip install coveralls
+  - travis_retry pip install coverage
 script:
-  tox
+  - tox
 after_success:
-- coveralls
+  - coveralls