Add better assert, remove stdout/err redirect

tests/integration/test_buildrequire_invalid_module.py

@@ -4,7 +4,11 @@ import pytest
 from sh import ErrorReturnCode
 
 
-def test_buildrequire_module_not_in_tag(pkg_util, scenario, repo, koji):
+# expected error message
+CANNOT_FIND_ANY_MODULE_BUILDS = "Cannot find any module builds"  # ...
+
+
+def test_buildrequire_invalid_module(pkg_util, scenario, repo, koji):
     """
         Run a build with with an invalid 'build_require' module.
         I.e.: required module is picked in such a way,
@@ -12,30 +16,30 @@ def test_buildrequire_module_not_in_tag(pkg_util, scenario, repo, koji):
         see platform's modulemd file and its 'koji_tag_with_modules' attribute
         (e.g.: platform: el-8.1.0 --> rhel-8.1.0-modules-build).
 
-        Koji resolver is expected to not be able to satisfy this build requirement and hence fail the build.
+        Koji resolver is expected to not be able to satisfy this build requirement
+        and hence fail the build.
 
         Assert that:
-        * the module build hasn't been accepted by MBS - rhpkg utility returns something else than 0
+        * the module build hasn't been accepted by MBS:
+          rhpkg utility returns something else than 0
+        * "Cannot find any module build..." found on STDERR
 
         If assert fails:
-        * cancel all triggered module builds
+        * cancel all triggered module builds.
 
         """
 
     repo.bump()
 
     try:
-        builds = pkg_util.run(
-            "--optional",
-            "rebuild_strategy=all"
-        )
+        builds = pkg_util.run("--optional", "rebuild_strategy=all")
 
         for build in builds:
             print("Canceling module-build {}...".format(build.id))
             pkg_util.cancel(build)
 
-        pytest.fail("build_require satisfied and module build accepted by MBS!")
+        pytest.fail("Invalid 'build_require' was satisfied and module build was accepted by MBS!")
 
     except ErrorReturnCode as e:
-        # expected outcome is that build submission fails
-        pass
+        # expected outcome: build submission fails
+        assert CANNOT_FIND_ANY_MODULE_BUILDS in e.stderr.decode("utf-8")

tests/integration/utils.py

@@ -167,7 +167,11 @@ class PackagingUtility:
 
     def __init__(self, packaging_utility, mbs_api):
         self._packaging_utility = Command(packaging_utility).bake(
-            _out=sys.stdout, _err=sys.stderr, _tee=True
+            # review: is redirect necessary?
+            # In case of failure, I can't find the stderr in the resulting exception object..
+            #_out=sys.stdout,
+            #_err=sys.stderr,
+            _tee=True
         )
         self._mbs_api = mbs_api