TestKit: check package build is free of errors and warnings (#1152)

Author: robsdedude

testkit/build.py

@@ -20,7 +20,11 @@
 
 
 if __name__ == "__main__":
-    run_python(["-m", "pip", "install", "-U", "pip"], warning_as_error=False)
+    run_python(
+        ["-m", "pip", "install", "-U", "pip", "build"],
+        warning_as_error=False,
+    )
+    run_python(["-m", "build", "."], warning_as_error=True)
     run_python(
         ["-m", "pip", "install", "-Ur", "requirements-dev.txt"],
         warning_as_error=False,