diff --git a/plugins/builder/osbuild.py b/plugins/builder/osbuild.py
index e6b6922..3853fc0 100644
--- a/plugins/builder/osbuild.py
+++ b/plugins/builder/osbuild.py
@@ -272,13 +272,13 @@ class OAuth2(requests.auth.AuthBase):
     """
 
     class Token:
-        def __init__(self, data):
+        def __init__(self, data, created):
             self.data = data["access_token"]
             self.type = data["token_type"]
             self.expires_in = int(data["expires_in"])
             self.scope = data.get("scope")
 
-            self.created = time.time()
+            self.created = created
 
         @property
         def expired(self) -> bool:
@@ -299,6 +299,11 @@ def token_expired(self) -> bool:
         return not self.token or self.token.expired
 
     def fetch_token(self, http: requests.Session):
+        # Set token creation time here. If we set it after the request was
+        # fulfilled, it would be offsetted by the time it took the token to
+        # get from the server here, which can result into us refreshing
+        # the token late.
+        token_created = time.time()
         data = {
             "grant_type": "client_credentials",
             "client_id": self.id,
@@ -312,7 +317,7 @@ def fetch_token(self, http: requests.Session):
             raise koji.GenericError(msg) from None
 
         token_data = res.json()
-        self.token = self.Token(token_data)
+        self.token = self.Token(token_data, token_created)
 
     def __call__(self, r: requests.Request):
         """Called by requests to obtain authorization"""
@@ -519,7 +524,7 @@ def attach_logs(self, compose_id: str, ireqs: List[ImageRequest]):
 
         ilogs = zip(logs.image_logs, ireqs)
         for log, ireq in ilogs:
-            name = "%s-%s.log" % (ireq.architecture, ireq.image_type)
+            name = f"{ireq.architecture}-{ireq.image_type}.log"
             self.logger.debug("Uploading logs: %s", name)
             self.upload_json(log, name)
 
@@ -534,7 +539,7 @@ def attach_manifests(self, compose_id: str, ireqs: List[ImageRequest]):
 
         imanifests = zip(manifests, ireqs)
         for manifest, ireq in imanifests:
-            name = "%s-%s.manifest" % (ireq.architecture, ireq.image_type)
+            name = f"{ireq.architecture}-{ireq.image_type}.manifest"
             self.logger.debug("Uploading manifest: %s", name)
             self.upload_json(manifest, name)
 
diff --git a/plugins/cli/osbuild.py b/plugins/cli/osbuild.py
index ff167f3..ae6527c 100755
--- a/plugins/cli/osbuild.py
+++ b/plugins/cli/osbuild.py
@@ -93,12 +93,11 @@ def check_target(session, name):
 
     target = session.getBuildTarget(name)
     if not target:
-        raise koji.GenericError("Unknown build target: %s" % name)
+        raise koji.GenericError(f"Unknown build target: {name}")
 
     tag = session.getTag(target['dest_tag'])
     if not tag:
-        raise koji.GenericError("Unknown destination tag: %s" %
-                                target['dest_tag_name'])
+        raise koji.GenericError(f"Unknown destination tag: {target['dest_tag_name']}")
 
 
 # pylint: disable=too-many-branches
@@ -161,8 +160,8 @@ def handle_osbuild_image(options, session, argv):
     task_id = session.osbuildImage(name, version, distro, image_types, target, arch, opts=opts)
 
     if not options.quiet:
-        print("Created task: %s" % task_id)
-        print("Task info: %s/taskinfo?taskID=%s" % (options.weburl, task_id))
+        print(f"Created task: {task_id}")
+        print(f"Task info: {options.weburl}/taskinfo?taskID={task_id}")
 
     # pylint: disable=protected-access
     if (args.wait is None and kl._running_in_bg()) or args.wait is False:
diff --git a/test/integration/test_koji.py b/test/integration/test_koji.py
index 50e728f..779f82b 100644
--- a/test/integration/test_koji.py
+++ b/test/integration/test_koji.py
@@ -39,7 +39,7 @@ def koji_command(*args, _input=None, _globals=None, **kwargs):
 
 def parse_os_release():
     info = {}
-    with open("/etc/os-release") as f:
+    with open("/etc/os-release", encoding="utf-8") as f:
         for line in f:
             line = line.strip()
             if not line:
diff --git a/test/run-builder.sh b/test/run-builder.sh
index 86d47a8..e8c35bd 100755
--- a/test/run-builder.sh
+++ b/test/run-builder.sh
@@ -22,7 +22,12 @@ else
 fi
 
 builder_start() {
-  GATEWAY_IP=$(${CONTAINER_RUNTIME} network inspect org.osbuild.koji | jq -r ".[0].plugins[0].ipam.ranges[0][0].gateway")
+  source /etc/os-release
+  if [[ $ID == rhel ]]; then
+    GATEWAY_IP=$(${CONTAINER_RUNTIME} network inspect org.osbuild.koji | jq -r ".[0].subnets[0].gateway")
+  else
+    GATEWAY_IP=$(${CONTAINER_RUNTIME} network inspect org.osbuild.koji | jq -r ".[0].plugins[0].ipam.ranges[0][0].gateway")
+  fi
   echo "Gateway IP is $GATEWAY_IP"
 
   # maybe copy the 'builder' plugin to the share dir
diff --git a/test/unit/test_builder.py b/test/unit/test_builder.py
index adf05e7..890335a 100644
--- a/test/unit/test_builder.py
+++ b/test/unit/test_builder.py
@@ -478,7 +478,7 @@ def creator():
 
         with tempfile.TemporaryDirectory() as tmp:
             cfgfile = os.path.abspath(os.path.join(tmp, "ko.cfg"))
-            with open(cfgfile, 'w') as f:
+            with open(cfgfile, 'w', encoding="utf-8") as f:
                 config.write(f)
 
             self.plugin.DEFAULT_CONFIG_FILES = [cfgfile]