Also require pytest < 8.0.0 in setup.cfg

setup.cfg

@@ -55,7 +55,7 @@ dev =
 	matplotlib>=3.1.1
 	flake8>=3.7.9
 	doc8>=0.8.0
-	pytest>=5.2.2
+	pytest>=5.2.2,<8.0.0
 	pytest-cov>=2.8.1
 	pytest-mock>=1.13.0
 	pytest-sugar>=0.9.2