portage error

# FEATURES=-sandbox emerge portage
Calculating dependencies... done!

>>> Verifying ebuild manifests

>>> Emerging (1 of 1) sys-apps/portage-2.1.11.17
 * portage-2.1.11.17.tar.bz2 SHA256 SHA512 WHIRLPOOL size ;-) ...                                                                                                                        [ ok ]
>>> Unpacking source...
>>> Unpacking portage-2.1.11.17.tar.bz2 to /var/tmp/portage/sys-apps/portage-2.1.11.17/work
>>> Source unpacked in /var/tmp/portage/sys-apps/portage-2.1.11.17/work
>>> Preparing source in /var/tmp/portage/sys-apps/portage-2.1.11.17/work/portage-2.1.11.17 ...
 * Setting portage.VERSION to 2.1.11.17 ...
patching file make.conf
Hunk #1 succeeded at 22 (offset -1 lines).
Hunk #2 succeeded at 44 with fuzz 2 (offset 6 lines).
Hunk #3 succeeded at 106 (offset 15 lines).
patch: setting attributes for ./make.conf.oHMvy7E: Operation not supported
 * ERROR: sys-apps/portage-2.1.11.17 failed (prepare phase):
 *   Failed to patch make.conf.example
 *
 * Call stack:
 *     ebuild.sh, line  85:  Called src_prepare
 *   environment, line 4847:  Called die
 * The specific snippet of code:
 *           patch make.conf "make.conf.${ARCH}".diff || die "Failed to patch make.conf.example";
 *
 * If you need support, post the output of `emerge --info '=sys-apps/portage-2.1.11.17'`,
 * the complete build log and the output of `emerge -pqv '=sys-apps/portage-2.1.11.17'`.
 * The complete build log is located at '/var/tmp/portage/sys-apps/portage-2.1.11.17/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/sys-apps/portage-2.1.11.17/temp/environment'.
 * Working directory: '/var/tmp/portage/sys-apps/portage-2.1.11.17/work/portage-2.1.11.17/cnf'
 * S: '/var/tmp/portage/sys-apps/portage-2.1.11.17/work/portage-2.1.11.17'

>>> Failed to emerge sys-apps/portage-2.1.11.17, Log file:

>>>  '/var/tmp/portage/sys-apps/portage-2.1.11.17/temp/build.log'

 * Messages for package sys-apps/portage-2.1.11.17:

 * ERROR: sys-apps/portage-2.1.11.17 failed (prepare phase):
 *   Failed to patch make.conf.example
 *
 * Call stack:
 *     ebuild.sh, line  85:  Called src_prepare
 *   environment, line 4847:  Called die
 * The specific snippet of code:
 *           patch make.conf "make.conf.${ARCH}".diff || die "Failed to patch make.conf.example";
 *
 * If you need support, post the output of `emerge --info '=sys-apps/portage-2.1.11.17'`,
 * the complete build log and the output of `emerge -pqv '=sys-apps/portage-2.1.11.17'`.
 * The complete build log is located at '/var/tmp/portage/sys-apps/portage-2.1.11.17/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/sys-apps/portage-2.1.11.17/temp/environment'.
 * Working directory: '/var/tmp/portage/sys-apps/portage-2.1.11.17/work/portage-2.1.11.17/cnf'
 * S: '/var/tmp/portage/sys-apps/portage-2.1.11.17/work/portage-2.1.11.17'