这次升级原本并不引人注目，最后却失败了，并让我在提示符下结束了升级。重启后，我的 WiFi 设备上没有 WiFi。然后，apt get update / upgrade 警告我纠正一些用户合并问题；之前在升级过程中已经让我失望的问题：
The following packages have been kept back:
apport apport-kde guile-2.2-libs python3-apport python3-problem-report
0 upgraded, 0 newly installed, 0 to remove and 5 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] y
Setting up usrmerge (25ubuntu2) ...
Smartmatch is experimental at /usr/lib/usrmerge/convert-usrmerge line 172.
cp: cannot create regular file '/usr/opt/lib/libmediaclient.so': No such file or directory
FATAL ERROR:
cp --no-dereference --preserve=all --reflink=auto --sparse=always /opt/lib/libmediaclient.so /usr/opt/lib/libmediaclient.so: rc=1
You can try correcting the errors reported and running again
/usr/lib/usrmerge/convert-usrmerge until it will complete without errors.
Do not install or update other Debian packages until the program
has been run successfully.
dpkg: error processing package usrmerge (--configure):
installed usrmerge package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
usrmerge
E: Sub-process /usr/bin/dpkg returned an error code (1)
出了什么问题？我该怎么办？