update dev dep (#26)

Author: kigawas

poetry.lock

@@ -16,12 +16,12 @@ mnemonic = "^0.19"
 pysha3 = "^1.0.2"
 
 [tool.poetry.dev-dependencies]
-black = "^19.10b0"
-mypy = "^0.770"
-flake8 = "^3.8.2"
-ipython = { version = "^7.14.0", python = "^3.6.8" }
-pytest = "^5.4.2"
-pytest-cov = "^2.9.0"
+black = "^20.8b0"
+mypy = "^0.782"
+flake8 = "^3.8.3"
+ipython = { version = "^7.18.0", python = "^3.7" }
+pytest = "^6.0.2"
+pytest-cov = "^2.10.1"
 
 [build-system]
 requires = ["poetry>=0.12"]