fix: Update noxfile and dependencies

Update dependencies, update minimal python version to 3.6.1
Fix noxfile, generate constraint file using constraint format add
`--without-hashes` option to be able to install dependencies, see:
python-poetry/poetry#3472 (comment)

noxfile.py

@@ -17,8 +17,10 @@ def install_with_constraints(
         session.run(
             "poetry",
             "export",
-            "--dev",
-            "--format=requirements.txt",
+            "--with",
+            "dev",
+            "--without-hashes",
+            "--format=constraints.txt",
             f"--output={requirements.name}",
             external=True,
         )
@@ -28,7 +30,7 @@ def install_with_constraints(
 @nox.session(python=PYTHON_VERSIONS)
 def tests(session: Session) -> None:
     args = session.posargs or ["--cov"]
-    session.run("poetry", "install", "--no-dev", external=True)
+    session.run("poetry", "install", "--only", "main", external=True)
     install_with_constraints(session, "coverage[toml]", "pytest", "pytest-cov")
     session.run("pytest", *args)