PEP 739: update rejected ideas text

Signed-off-by: Filipe Laíns <lains@riseup.net>

peps/pep-0739.rst

@@ -724,15 +724,27 @@ JSON Schema
 Rejected Ideas
 ==============
 
-Having a larger scope
----------------------
+Including environment-specific data
+-----------------------------------
 
 One of the main requests in the discussion of this PEP was the inclusion of
 other kind of information, such as the ``site-packages`` path. It is the opinion
 of the PEP authors that information regarding the Python environment should be
-provided by a separate file, creating the a clear separation between the build
-details, which should be immutable across any interpreter instance, and details
-that can change, such as environment details.
+provided by a separate file.
+
+Including environment-specific data in the config file means that it would be
+environment-specific, so virtual environments would need their own config file.
+This is problematic because virtual environments survive updates of the base
+Python installation, creating the possibily for the static config file to be
+outdated, and making its data unreliable, which defeats its purpose.
+
+The proposed solution, partially implemented in this PEP, is to have a
+``build-details.json`` file, referent to the base Python installation, and a
+``environment.json`` file, referent to the specific environment.
+
+With ``build-details.json`` being part of the Python distribution, when the base
+Python installation gets updated, ``build-details.json`` does too, ensuring the
+static description files are never outdated.
 
 
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