add support for python 3.9

Signed-off-by: Bryant Finney <bryant@outdoorlinkinc.com>

Pipfile

@@ -7,7 +7,7 @@ verify_ssl = true
 black = { version = "~=20.8b1", markers = "python_version >= '3.6'" }
 pipenv-setup = { editable = true, path = "." }
 pytest = { markers = "python_version>='3.6'", version = "~=5.2" }
-pytest-mypy = { markers = "python_version>='3.5'", version = "~=0.3" }
+pytest-mypy = { markers = "python_version>='3.5'", version = ">=0.3" }
 pytest-cov = "~=2.7"
 pytest-datadir = "~=1.3"
 pytest-xdist = "~=1.29"

setup.py

@@ -136,14 +136,14 @@
     # https://packaging.python.org/en/latest/requirements.html
     extras_require={
         "dev": [
+            "black~=20.8b1; python_version >= '3.6'",
             "pytest~=5.2; python_version >= '3.6'",
-            "pytest-mypy~=0.3; python_version >= '3.5'",
+            "pytest-mypy>=0.3; python_version >= '3.5'",
             "pytest-cov~=2.7",
             "pytest-datadir~=1.3",
             "pytest-xdist~=1.29",
             "tox~=3.14",
             "autopep8~=1.4",
-            "black~=20.8b1; python_version >= '3.6'",
         ]
     },
     install_requires=[

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27, py35, py36, py37, py38
+envlist = py27, py35, py36, py37, py38, py39
 skip_missing_interpreters=true
 
 [testenv]
@@ -12,7 +12,11 @@ commands =
     ; tip: tox -- -n PROCESS_COUNT to speed up with multi-processing
     pytest --cov=pipenv_setup {posargs}
 
-; only run codecov on python 3.7
+; only run mypy on python 3.7 and 3.9
 [testenv:py37]
 commands =
-    pytest --cov=pipenv_setup --mypy {posargs}
+    pytest --cov=pipenv_setup --mypy {posargs}
+
+[testenv:py39]
+commands =
+    pytest --cov=pipenv_setup --mypy {posargs}