Add "coverage < 5.0" to setup.py to enforce it because coveralls does…

… not currently support coverage 5.0+ per TheKevJames/coveralls-python#203

setup.py

@@ -70,7 +70,18 @@ def package_vars(version_file):
     py_modules=[splitext(basename(path))[0] for path in glob("src/*.py")],
     include_package_data=True,
     install_requires=["docopt", "setuptools"],
-    extras_require={"test": ["pre-commit", "pytest", "pytest-cov", "coveralls"]},
+    extras_require={
+        "test": [
+            "pre-commit",
+            "coveralls",
+            # coveralls does not currently support coverage 5.0
+            # https://github.com/coveralls-clients/coveralls-python/issues/203
+            # is the issue for this on the coveralls project
+            "coverage < 5.0",
+            "pytest-cov",
+            "pytest",
+        ]
+    },
     # Conveniently allows one to run the CLI tool as `example`
     entry_points={"console_scripts": ["example = example.example:main"]},
 )