makepackage: fix error building macOS package for Python 3.x only

makepanda/makepackage.py

@@ -473,7 +473,7 @@ def MakeInstallerOSX(version, runtime=False, python_versions=[], **kwargs):
 
     dmg_name = "Panda3D-" + version
     if len(python_versions) == 1 and not python_versions[0]["version"].startswith("2."):
-        dmg_name += "-py" + pyver
+        dmg_name += "-py" + python_versions[0]["version"]
     dmg_name += ".dmg"
 
     if (os.path.isfile(dmg_name)): oscmd("rm -f %s" % dmg_name)