python3: Document shortcomings of pkg_alternatives that make this package necessary at the moment

[Jason Bacon <bacon%NetBSD.org@localhost>]

Module Name:	pkgsrc-wip
Committed By:	Jason Bacon <bacon%NetBSD.org@localhost>
Pushed By:	outpaddling
Date:		Tue Feb 15 12:53:05 2022 -0600
Changeset:	bf7f2edbcf538eb5a367fd63f4a6e1b408e42b5d

Modified Files:
	python3/DESCR

Log Message:
python3: Document shortcomings of pkg_alternatives that make this
package necessary at the moment

To see a diff of this commit:
https://wip.pkgsrc.org/cgi-bin/gitweb.cgi?p=pkgsrc-wip.git;a=commitdiff;h=bf7f2edbcf538eb5a367fd63f4a6e1b408e42b5d

Please note that diffs are not public domain; they are subject to the
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diffstat:
 python3/DESCR | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diffs:
diff --git a/python3/DESCR b/python3/DESCR
index c369faa274..00d97657cb 100644
--- a/python3/DESCR
+++ b/python3/DESCR
@@ -16,3 +16,17 @@ documentation for hints.
 This is a wrapper package for installing the default python 3
 version and links to bin/python3 and bin/python, for running
 python scripts not installed by pkgsrc, but using pkgsrc python.
+
+Currently, pkg_alternatives does not seem to have the ability
+to keep python and python3 linked to the default python version.
+Instead, it links to the latest installed version.  This causes
+python scripts using #!/usr/bin/env python or #!/usr/bin/python3
+(i.e. scripts not installed by pkgsrc) to suddenly stop working
+when a python newer than the default is installed, because they
+cannot find modules installed by pkgsrc using the default version.
+pkg_altneratives has the ability to lock the links to a specific
+version, but this causes breakage when the default version changes
+and packages are updated.
+
+This wrapper package solves these problems by keeping bin/python
+and bin/python3 linked to the default python version at all times.