string comparison fix for zsh

[jefemagril]

My Mac terminal running the built-in zsh was throwing an error when doing string comparison with double equals ==. Changing it to single = made it work. I believe it's also completely fine on bash as well that way.

[daschuer]

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[jefemagril]

@daschuer I signed it

[daschuer]

Thank you. This is also an issue in the 2.6 branch. Can you rebase your fix to that. I think it is

git rebase --onto=upstream/2.6 HEAD~1