BF: Env vars must be strings

share/fsl/sbin/update_fsl_package

@@ -551,7 +551,7 @@ def install_packages(packages : Sequence[Package], dry_run : bool):
     # $FSLDIR/share/fsl/sbin/createFSLWrapper for
     # more details.
     env = os.environ.copy()
-    env['FSL_CREATE_WRAPPER_SCRIPTS'] = 1
+    env['FSL_CREATE_WRAPPER_SCRIPTS'] = '1'
 
     print('\nInstalling packages...')
     if dry_run: