“Interrupted by header callback: Server reports Content-Length”如何解决

mock初始化时的错误信息如下：

Downloading Packages:
[SKIPPED] systemd--.fc25.x86_64.rpm: Already downloaded
[SKIPPED] systemd-pam--.fc25.x86_64.rpm: Already downloaded
[MIRROR] lightdm-1.18.-1.1.fc25.x86_64.rpm: Interrupted by header callback: Server reports Content-Length:  but expected size is:
[FAILED] lightdm-1.18.-1.1.fc25.x86_64.rpm: No more mirrors to try - All mirrors were already tried without success
(-/): lightdm-gob % [=============       ] 1.9 MB/s | 3.4 MB     : ETA
Error: Error downloading packages:
  Cannot download v2./lightdm-1.18.-1.1.fc25.x86_64.rpm: All mirrors were tried

 [FAIL]
 [版本构建失败]          构建 lightdm-cgdl-greeter-1.0-.fc25.src.rpm 失败! 请检查构建日志 /cgdl/desktop/jenkins/workspace/CGDL/CGDL-v2.-sys-base-related/CGDL-v2.-sys-base-related-dev-build/version-build-related/../build-x86_64/v2.//log//verbuild//rpm_error.log
 [构建失败] verbuild 退出，请查看构建日志：/cgdl/desktop/jenkins/workspace/CGDL/CGDL-v2.-sys-base-related/CGDL-v2.-sys-base-related-dev-build/version-build-related/../build-x86_64/v2.//log//std_build.log 

原因分析：

1、期望的大小和实际包大小不一致，说明仓库获取时存在问题；由三种可能性：1> mock配置文件配置的仓库地址不正确，而安装mock依赖包时的实际数据与缓存中数据不一致；   2> mock配置的yum仓库存在过期缓存；3> 仓库目录下存在临时隐藏目录.repodata   4> mock配置的dnf仓库存在过期缓存；

解决办法：

1、修正mock配制文件的yum源地址；

2、dnf clean expire-cache

3、删除临时隐藏目录

备注：linux下查找缓存下是否有checksum不一致的包

[root@localhost os]# find /var/cache/ -name "python3-rpm*"
/var/cache/mock/desktop-v2.1-i386-release-sys-base-related/dnf_cache/desktop-32-update-f468bc6a55692839/packages/python3-rpm-4.13.0.1-1.1.fc25.i686.rpm
/var/cache/mock/desktop-v2.1-i386-release-wine-related/dnf_cache/desktop-32-update-f468bc6a55692839/packages/python3-rpm-4.13.0.1-1.1.fc25.i686.rpm
/var/cache/mock/desktop-v2.1-i386-release-software-center-related/dnf_cache/desktop-os-e21f8ca340c4e99c/packages/python3-rpm-macros-3-12.fc25.noarch.rpm

删除相关包方法：

rm `find /var/cache/ -name "python3-rpm*"`

将关于涉事包的所有mock缓存全部删除后，再次执行构建，成功；初步判定系统mock缓存目录下不同mock环境的缓存数据会相互影响。具体根因后面进一步跟进分析