tracetool: fix usage of try_import()

try_import returns a tuple of a boolean and the requested module or attribute.
exists() functions return tracetool.try_import("tracetool.format." + name)[1]
but they should return the boolean value instead.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250929154938.594389-2-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/scripts/tracetool/backend/__init__.py b/scripts/tracetool/backend/__init__.py
index 7bfcc86..6c6344d 100644
--- a/scripts/tracetool/backend/__init__.py
+++ b/scripts/tracetool/backend/__init__.py
@@ -94,7 +94,7 @@ def exists(name):
     if name == "nop":
         return True
     name = name.replace("-", "_")
-    return tracetool.try_import("tracetool.backend." + name)[1]
+    return tracetool.try_import("tracetool.backend." + name)[0]
 
 
 class Wrapper:
diff --git a/scripts/tracetool/format/__init__.py b/scripts/tracetool/format/__init__.py
index 2dc46f3..042fe7d 100644
--- a/scripts/tracetool/format/__init__.py
+++ b/scripts/tracetool/format/__init__.py
@@ -70,7 +70,7 @@ def exists(name):
     if len(name) == 0:
         return False
     name = name.replace("-", "_")
-    return tracetool.try_import("tracetool.format." + name)[1]
+    return tracetool.try_import("tracetool.format." + name)[0]
 
 
 def generate(events, format, backend, group):