Fixed a missing sys.exit

doc/makepanda/makepanda.py

@@ -915,7 +915,7 @@ srcdir1 = os.path.join(__path__[0], 'src')
 srcdir2 = os.path.join(__path__[0], '..', '..', 'direct', 'src')
 if    (os.path.isdir(srcdir1)): __path__[0] = srcdir1
 elif  (os.path.isdir(srcdir2)): __path__[0] = srcdir2
-else: exit("Cannot find the 'direct' tree")
+else: sys.exit("Cannot find the 'direct' tree")
 """
 
 if (PkgSkip("PYTHON")==0):