integration test, enforce min python for non-pip install

.appveyor.yml

@@ -16,4 +16,4 @@ init:
 
 install: pip install -e .[tests]
 
-test_script: pytest -rsv
+test_script: pytest -r a -v

.travis.yml

@@ -13,6 +13,15 @@ python:
 matrix:
   include:
   - os: linux
+    name: Integration install
+    install:
+    - python setup.py install
+    - pip install $(basename $TRAVIS_REPO_SLUG)[tests]
+    script:
+    - cd $HOME
+    - python -m pytest $TRAVIS_BUILD_DIR -r a -v
+  - os: linux
+    name: PEP8 MyPy Coverage
     python: 3.7
     install: pip install -e .[tests,cov]
     script:
@@ -24,4 +33,4 @@ matrix:
 
 install: pip install -e .[tests]
 
-script: pytest -v
+script: pytest -r a -v

pyproject.toml

@@ -0,0 +1,2 @@
+[build-system]
+requires = ["setuptools", "wheel"]

setup.cfg

@@ -26,9 +26,6 @@ long_description_content_type = text/markdown
 
 [options]
 python_requires = >= 3.6
-setup_requires =
-  setuptools >= 38.6
-  pip >= 10
 packages = find:
 scripts =
   meld_all.py

setup.py

@@ -1,3 +1,8 @@
 #!/usr/bin/env python
-from setuptools import setup
-setup()
+import setuptools
+import sys
+
+if sys.version_info < (3, 6):
+    raise SystemExit("Python >= 3.6 required")
+
+setuptools.setup()