On 2020-08-28 12:33:07 +0430 (+0430), mahdi abbasi wrote: [...]

When i want install horizon with pip3 i recieve and error:

Could not satisfy constraints for horizon: installation from path or url cannot be constrained to a version. [...]

This sounds like you're passing a -c option to pip telling it to apply a constraints file, but you're attempting to install Horizon from source instead of from a released package so it can't be matched against the constraints list. The easy workaround is to delete the Horizon entry from the constraints list you're using, or consume a release of Horizon from PyPI instead of using a source checkout. -- Jeremy Stanley