[PATCH v7 2/8] Acceptance tests: introduce utility method for tags unique vals

[Cleber Rosa <crosa@redhat.com>]

Currently a test can describe the target architecture binary that it
should primarily be run with, be setting a single tag value.

The same approach is expected to be done with other QEMU aspects to be
tested, for instance, the machine type and accelerator, so let's
generalize the logic into a utility method.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
---
 tests/acceptance/avocado_qemu/__init__.py | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/tests/acceptance/avocado_qemu/__init__.py b/tests/acceptance/avocado_qemu/__init__.py
index 9a57c020d8..e676d9c4e7 100644
--- a/tests/acceptance/avocado_qemu/__init__.py
+++ b/tests/acceptance/avocado_qemu/__init__.py
@@ -100,14 +100,21 @@ def exec_command_and_wait_for_pattern(test, command,
 
 
 class Test(avocado.Test):
+    def _get_unique_tag_val(self, tag_name):
+        """
+        Gets a tag value, if unique for a key
+        """
+        vals = self.tags.get(tag_name, [])
+        if len(vals) == 1:
+            return vals.pop()
+        return None
+
     def setUp(self):
         self._vms = {}
-        arches = self.tags.get('arch', [])
-        if len(arches) == 1:
-            arch = arches.pop()
-        else:
-            arch = None
-        self.arch = self.params.get('arch', default=arch)
+
+        self.arch = self.params.get('arch',
+                                    default=self._get_unique_tag_val('arch'))
+
         default_qemu_bin = pick_default_qemu_bin(arch=self.arch)
         self.qemu_bin = self.params.get('qemu_bin',
                                         default=default_qemu_bin)
-- 
2.21.0