Description of problem:
Running translatesieve on sieve scripts migrated from cyrus-imapd 2.4 as advised in upgrade documentation (due to change in default altnamespace) fails as it tries to run on the wrong directory. Running with translatesieve from a configured and made but not installed 3.0.15 works fine, although I have not been able to find a corresponding bugfix at Cyrus.

Version-Release number of selected component (if applicable):
3.0.7

How reproducible:
On my system I replicated cyrus mailstores from the Cyrus 2.4 server (on CentOS 7) to the Cyrus 3.0 server (on RHEL8) which copies over the sieve scripts to /var/lib/imap/sieve. Replication should not be needed though, as long as the original scripts are there. The old server had fileinto commands working under a 'altnamespace: 0' system, so used INBOX/ formats for folders. As I already had unixhierarchysep: 1, so the correct command is "translatesieve -n -u" for a dry run. Leaving off the -n produces a FATAL error as expected.

Steps to Reproduce:
1. have some sieve scripts in /var/lib/imap/sieve, and a functional RHEL-package installed cyrus-imapd 3.0.7
2. run the translatesieve script with -n for dry run (has to be run as cyrus user)
3. observe error...

Actual results:
bash-4.4$  /usr/libexec/cyrus-imapd/translatesieve -u -n
you are using /var/lib/imap/sieve as your sieve directory.
translating sievedir /var/lib/imap/sieve... not converting separator.
converting name space from traditional to alternative.
error: couldn't chdir to portables
error: couldn't chdir to private
error: couldn't chdir to tpm
error: couldn't chdir to polkit-1
error: couldn't chdir to rsyslog
error: couldn't chdir to NetworkManager
error: couldn't chdir to setroubleshoot
error: couldn't chdir to udisks2
error: couldn't chdir to rhsm
error: couldn't chdir to mlocate
error: couldn't chdir to postfix

Expected results:
...would be what I get when running with the translatesieve from 3.0.15: (ignore the described changes, as I have already converted these scripts it would mess it up if I actually ran it again).
bash-4.4$ /opt/cyrus-imapd-3.0.15/tools/translatesieve -u -n
you are using /var/lib/imap/sieve as your sieve directory.
translating sievedir /var/lib/imap/sieve... not converting separator.
converting name space from traditional to alternative.
translating ingo.script...
translating ingo.script...
<     fileinto "Spam";
>     fileinto "Shared Folders/Spam";
translating ingo.script...
<     fileinto "Spam";
>     fileinto "Shared Folders/Spam";
...etc...

Additional info: