ci: test oldest supported attrs

Author: blueyed

.travis.yml

@@ -49,8 +49,9 @@ jobs:
     # - pytester's LsofFdLeakChecker
     # - TestArgComplete (linux only)
     # - numpy
+    # - old attrs
     # Empty PYTEST_ADDOPTS to run this non-verbose.
-    - env: TOXENV=py37-lsof-numpy-twisted-xdist PYTEST_COVERAGE=1 PYTEST_ADDOPTS=
+    - env: TOXENV=py37-lsof-oldattrs-numpy-twisted-xdist PYTEST_COVERAGE=1 PYTEST_ADDOPTS=
 
     # Specialized factors for py37.
     # Coverage for:

setup.py

@@ -5,7 +5,7 @@
 INSTALL_REQUIRES = [
     "py>=1.5.0",
     "packaging",
-    "attrs>=17.4.0",
+    "attrs>=17.4.0",  # should match oldattrs tox env.
     "more-itertools>=4.0.0",
     "atomicwrites>=1.0",
     'pathlib2>=2.2.0;python_version<"3.6"',

tox.ini

@@ -41,6 +41,8 @@ setenv =
     xdist: _PYTEST_TOX_POSARGS_XDIST=-n auto
 extras = testing
 deps =
+    oldattrs: attrs==17.4.0
+    oldattrs: hypothesis<=4.38.1
     numpy: numpy
     pexpect: pexpect
     pluggymaster: git+https://github.com/pytest-dev/pluggy.git@master