Bench --site testsite install-app wiki => command not found

Hi everyone,

On my testsystem I want to install some more apps, but the commands always end with
$: command not found

I tried to install various apps, such as wiki or crm.
The first command works: bench get-app wiki
The second command is not found: bench --site testsite install-app wiki
testsite does exist and is running.

The following apps are already installed and working:
frappe 15.40.2 version-15
erpnext 15.34.1 version-15
hrms 16.0.0-dev develop
payments 0.0.1 develop
erpnext_germany 15.4.1 version-15
education 15.5.0 develop
lms 2.4.0 develop
hospitality 0.0.1 develop

Even the command “bench update” works. I have no clue what the problem is.
There is no entry in the log files.

I wonder what the issue is as some bench commands are executed.
Anyone having an idea what I need to do?

Thanks for your help.

After fiddling around with some Python packages (upgrading or downgrading them) as well as clearing the ERPNext cache, migrating the system, and restarting the system several times, I was able to install the apps I wanted.
I believe which made a difference was running the bench commands, which have not been found before with the addition of --verbose.
Still, I wonder what caused the problem, with command not found.
At least it works now.