Add fixture modifying grub config

* some systems are unable to boot to an older kernel due to missing
  setting in the grub config
* add a fixture fixing this

Signed-off-by: Daniel Diblik <[email protected]>

tests/integration/conftest.py

@@ -645,8 +645,53 @@ def _create_old_repo(distro: str, repo_name: str):
         f.write("gpgcheck=0\n")
 
 
+@pytest.fixture()
+def grub_kernel_settings(backup_directory, shell):
+    """
+    Fixture.
+    Set the grub config to be able to boot to different kernel.
+    """
+    grub_config = "/etc/default/grub"
+    grub_default_opt = "GRUB_DEFAULT"
+    grub_savedefault_opt = "GRUB_SAVEDEFAULT"
+    grub_default = f"{grub_default_opt}=saved"
+    grub_savedefault = f"{grub_savedefault_opt}=true"
+
+    # Read the current content of the grub config
+    with open(grub_config, "r") as file:
+        lines = file.readlines()
+        print(lines)
+
+    print(lines)
+
+    # Initialize flags to track if we need to add the settings
+    grub_default_set = False
+    grub_savedefault_set = False
+
+    # Modify the lines if the options are present
+    for i, line in enumerate(lines):
+        if line.startswith(grub_default_opt):
+            lines[i] = grub_default + "\n"
+            grub_default_set = True
+        if line.startswith(grub_savedefault_opt):
+            lines[i] = grub_savedefault + "\n"
+            grub_savedefault_set = True
+
+    # Append the options if they are not present
+    if not grub_default_set:
+        lines.append(f"\n{grub_default}\n")
+    if not grub_savedefault_set:
+        lines.append(f"\n{grub_savedefault}\n")
+
+    # Write the modified content back to the grub config
+    with open(grub_config, "w") as file:
+        file.writelines(lines)
+
+    yield
+
+
 @pytest.fixture(scope="function")
-def kernel(shell):
+def kernel(shell, grub_kernel_settings):
     """
     Install specific kernel version and configure
     the system to boot to it. The kernel version is not the