suppress pytest rewrite assertion warning

Author: ikappaki

CHANGELOG.md

@@ -6,6 +6,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+ * Suppress pytest assertion rewrite warning for basilisp when running `basilisp test` (#1252)
+
 ## [v0.4.0]
 ### Added
  * Added support for referring imported Python names as by `from ... import ...` (#1154)

src/basilisp/cli.py

@@ -745,6 +745,15 @@ def test(
             "Cannot run tests without dependency PyTest. Please install PyTest and try again.",
         )
     else:
+        # `basilisp` declares the testrunner as a pytest plugin, so
+        # pytest tries to import it for assertion rewriting.  Since
+        # it's already imported, pytest emits a warning. As rewriting
+        # isn't needed, we ignore it.
+        extra = [
+            "-W",
+            "ignore:Module already imported so cannot be rewritten:pytest.PytestAssertRewriteWarning",
+        ] + extra
+
         sys.exit(pytest.main(args=list(extra)))