Raise any warnings during pytest

Author: ConorMacBride

setup.cfg

@@ -42,6 +42,11 @@ test =
 
 [tool:pytest]
 testpaths = "tests"
+markers =
+    image: run test during image comparison only mode.
+    hash: run test during hash comparison only mode.
+filterwarnings =
+    error
 
 [flake8]
 max-line-length = 100

tox.ini

@@ -51,8 +51,3 @@ description = check code style, e.g. with flake8
 deps = pre-commit
 commands =
     pre-commit run --all-files
-
-[pytest]
-markers =
-    image: run test during image comparison only mode.
-    hash: run test during hash comparison only mode.