fix(log): add the stdio log if it doesn't exist

Signed-off-by: Raito Bezarius <raito@lix.systems>

buildbot_nix/__init__.py

@@ -496,9 +496,13 @@ class NixConfigure(buildstep.CommandMixin, steps.BuildStep):
         self.observer = logobserver.BufferLogObserver()
         self.addLogObserver("stdio", self.observer)
 
+
     @defer.inlineCallbacks
     def run(self) -> Generator[Any, object, Any]:
+        try:
             configure_log: Log = yield self.getLog("stdio")
+        except Exception:
+            configure_log: Log = yield self.addLog("stdio")
 
         # Takes precedence.
         configure_log.addStdout("checking if there's a .ci/buildbot.nix...")