note: some files have two versions in them, e.g.:
```
assert CffiRecipe._version == "1.15.1"
class CffiRecipePinned(util.InheritedRecipeMixin, CffiRecipe):
version = "1.17.1"
```
The assert is left there as I think it might be useful to get a failure if we rebase p4a
and the upstream recipe version changes. There might be substantial changes in the upstream
recipe that we need to adapt to. In the happy case, if we rebase p4a, we just have to manually
update these asserts to the new versions at that time.
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