you write: "requirements.txt doesn't tell me which version of Python the code was developed with".
Do you expect to have less pain with any othe rlanguage with this situation?
C# for example - I had some compatibility issues between versions 2 and 3.1 of .NET Core, but at least the .csproj tells me what version it's supposed to be built with, and the LangVersion property indicates the version of C#.
https://doc.rust-lang.org/cargo/reference/manifest.html#the-...
tensorflow >=1.12,!=2.1.*