pyproject.toml: Add test and doc dependencies for Python 2 and 3

Author: tony

pyproject.toml

@@ -9,6 +9,30 @@ license = "MIT"
 python = "~2.7 || ^3.5"
 
 [tool.poetry.dev-dependencies]
+black = {version="==19.10b0", python="^3.6"}
+docutils = "*"
+flake8 = "*"
+isort = "*"
+pytest = [
+  {version="<4.7.0", python="<3"},
+  {version="*", python=">=3"}
+]
+pathlib2 = {version="<2.3.5", python="<3"}  # Untangle pytest peer-dependency
+sphinx = [
+  {version="<2", python="<3"},
+  {version="*", python=">=3"}
+]
+twine = "*"
+codecov = "*"
+coverage = "*"
+pytest-cov = [
+  {version="<2.10.0", python="<3"},
+  {version="*", python=">=3"}
+]
+pytest-mock = [
+  {version="<3.0.0", python="<3"},
+  {version="*", python=">=3"}
+]
 
 [build-system]
 requires = ["poetry>=0.12"]