Unable to access 'https://github.com/ematvey/pybacktest.git/': OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443

Hello!
When i wanted install a package
"pip install git+https://github.com/ematvey/pybacktest.git"
I got a error:
Fatal: unable to access 'https://github.com/ematvey/pybacktest.git/': OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443

What am i doing wrong?