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python.md: fix grammar around bdist_wheel FAQ

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giraffito 2018-03-21 19:57:52 +00:00 committed by GitHub
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doc/languages-frameworks/python.md
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@ -871,8 +871,10 @@ Executing `python setup.py bdist_wheel` in a `nix-shell `fails with
```
ValueError: ZIP does not support timestamps before 1980
```
This is because files are included that depend on items in the Nix store which have a timestamp of, that is, it corresponds to January the 1st, 1970 at 00:00:00. And as the error informs you, ZIP does not support that.
The command `bdist_wheel` takes into account `SOURCE_DATE_EPOCH`, and `nix-shell` sets this to 1. By setting it to a value corresponding to 1980 or later, or by unsetting it, it is possible to build wheels.
This is because files from the Nix store (which have a timestamp of the UNIX epoch of January 1, 1970) are included in the .ZIP, but .ZIP archives follow the DOS convention of counting timestamps from 1980.
The command `bdist_wheel` reads the `SOURCE_DATE_EPOCH` environment variable, which `nix-shell` sets to 1. Unsetting this variable or giving it a value corresponding to 1980 or later enables building wheels.
Use 1980 as timestamp:
```shell
@ -882,7 +884,7 @@ or the current time:
```shell
nix-shell --run "SOURCE_DATE_EPOCH=$(date +%s) python3 setup.py bdist_wheel"
```
or unset:
or unset `SOURCE_DATE_EPOCH`:
```shell
nix-shell --run "unset SOURCE_DATE_EPOCH; python3 setup.py bdist_wheel"
```