Use Python 3.11 as the default Python version for new apps

Previously if a new app did not specify a Python version via a
`runtime.txt` file or the appropriate `Pipfile` config option, then the
buildpack would default to the latest Python 3.10 release (currently
Python 3.10.10).

Now the buildpack will use the latest Python 3.11 release (currently
Python 3.11.2).

This does not affect:
* apps that specify an explicit Python version
* existing apps that have already had a build using the previous default
  version (since that version is remembered from one build to the next,
  via the "sticky versions" feature).

Use-cases involving new apps that aren't compatible with Python 3.11
will now need to specify Python 3.10 explicitly:
https://devcenter.heroku.com/articles/python-support#specifying-a-python-version

However most apps should be compatible, since Python 3.11 was released
several months ago (2022-10-24), does not contain significant breaking
changes over Python 3.10, and has been happily used by the
python-getting-started project since 2022-10-25.

GUS-W-12345720.

Author: edmorley

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Use Python 3.11 as the default Python version for new apps (previously Python 3.10) ([#1408](https://github.com/heroku/heroku-buildpack-python/pull/1408)).
 
 ## v225 (2023-02-08)
 

README.md

@@ -42,7 +42,7 @@ A `requirements.txt` must be present at the root of your application's repositor
 
 To specify your python version, you also need a `runtime.txt` file - unless you are using the default Python runtime version.
 
-Current default Python Runtime: Python 3.10.10
+Current default Python Runtime: Python 3.11.2
 
 Alternatively, you can provide a `setup.py` file, or a `Pipfile`.
 Using `pipenv` will generate `runtime.txt` at build time if one of the field `python_version` or `python_full_version` is specified in the `requires` section of your `Pipfile`.

bin/default_pythons

@@ -15,4 +15,4 @@ LATEST_36="python-3.6.15"
 LATEST_35="python-3.5.10"
 LATEST_34="python-3.4.10"
 LATEST_27="python-2.7.18"
-DEFAULT_PYTHON_VERSION="${LATEST_310}"
+DEFAULT_PYTHON_VERSION="${LATEST_311}"

spec/hatchet/nltk_spec.rb

@@ -12,7 +12,6 @@
           remote: -----> Downloading NLTK corpora…
           remote: -----> Downloading NLTK packages: city_database stopwords
           remote: .*: RuntimeWarning: 'nltk.downloader' found in sys.modules after import of package 'nltk', but prior to execution of 'nltk.downloader'; this may result in unpredictable behaviour
-          remote:   warn\\(RuntimeWarning\\(msg\\)\\)
           remote: \\[nltk_data\\] Downloading package city_database to
           remote: \\[nltk_data\\]     /tmp/build_.*/.heroku/python/nltk_data...
           remote: \\[nltk_data\\]   Unzipping corpora/city_database.zip.

spec/hatchet/stack_spec.rb

@@ -56,10 +56,10 @@
           remote: -----> No Python version was specified. Using the same version as the last build: python-#{DEFAULT_PYTHON_VERSION}
           remote:        To use a different version, see: https://devcenter.heroku.com/articles/python-runtimes
           remote: python: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.34' not found (required by python)
-          remote: python: /lib/x86_64-linux-gnu/libm.so.6: version `GLIBC_2.35' not found (required by /app/.heroku/python/lib/libpython3.10.so.1.0)
-          remote: python: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.33' not found (required by /app/.heroku/python/lib/libpython3.10.so.1.0)
-          remote: python: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.32' not found (required by /app/.heroku/python/lib/libpython3.10.so.1.0)
-          remote: python: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.34' not found (required by /app/.heroku/python/lib/libpython3.10.so.1.0)
+          remote: python: /lib/x86_64-linux-gnu/libm.so.6: version `GLIBC_2.35' not found (required by /app/.heroku/python/lib/libpython3.11.so.1.0)
+          remote: python: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.33' not found (required by /app/.heroku/python/lib/libpython3.11.so.1.0)
+          remote: python: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.32' not found (required by /app/.heroku/python/lib/libpython3.11.so.1.0)
+          remote: python: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.34' not found (required by /app/.heroku/python/lib/libpython3.11.so.1.0)
           remote: -----> Stack has changed from heroku-22 to heroku-20, clearing cache
           remote: -----> No change in requirements detected, installing from cache
           remote: -----> Installing python-#{DEFAULT_PYTHON_VERSION}

spec/spec_helper.rb

@@ -12,7 +12,7 @@
 LATEST_PYTHON_3_9 = '3.9.16'
 LATEST_PYTHON_3_10 = '3.10.10'
 LATEST_PYTHON_3_11 = '3.11.2'
-DEFAULT_PYTHON_VERSION = LATEST_PYTHON_3_10
+DEFAULT_PYTHON_VERSION = LATEST_PYTHON_3_11
 
 # Work around the return value for `default_buildpack` changing after deploy:
 # https://github.com/heroku/hatchet/issues/180