Switch to an older openssl package

brew switch openssl 1.0.2s

Or, depending on your exact system configuration, 
you may need to switch to a different version. 
Check the output of ls -al /usr/local/Cellar/openssl for the version number to switch to.

brew switch openssl 1.0.2q
# or
brew switch openssl 1.0.2r
# or 
brew switch openssl 1.0.2s
# or
brew switch openssl 1.0.2t
# etc...