all: Remove Python 2.7 support.

Python 2.7 has been EOL since January 2020.

Ubuntu oldoldlts (Focal Fossa, 20.04) has Python 3.8.  Debian oldoldstable
(Buster, from 2019) has Python 3.7.  RHEL 8 (from 2019) has Python 3.6.

It's easier than ever to install a modern Python using uv.

Given this, it seems like a fine idea to drop Python 2.7 support.

Even though the build is not tested on Python as old as 3.3, I left
comments stating that "3.3+" is the baseline Python version.  However, it
might make sense to bump this to e.g., 3.10, the oldest Python 3 version
used during CI. Or, using uv or another method actually test on the oldest
Python interpreter that is desirable to support (uv goes back to Python 3.7
easily; in October 2025, the oldest supported Python interpreter version
will be 3.10)

Signed-off-by: Jeff Epler <jepler@gmail.com>

.github/workflows/mpy_format.yml

@@ -15,7 +15,7 @@ concurrency:
 
 jobs:
   test:
-    runs-on: ubuntu-22.04 # use 22.04 to get python2
+    runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v5
     - name: Install packages

.github/workflows/ports_unix.yml

@@ -121,7 +121,7 @@ jobs:
       run: tests/run-tests.py --print-failures
 
   nanbox:
-    runs-on: ubuntu-22.04 # use 22.04 to get python2, and libffi-dev:i386
+    runs-on: ubuntu-22.04 # use 22.04 to get libffi-dev:i386
     steps:
     - uses: actions/checkout@v5
     - name: Install packages
@@ -135,7 +135,7 @@ jobs:
       run: tests/run-tests.py --print-failures
 
   longlong:
-    runs-on: ubuntu-22.04 # use 22.04 to get python2, and libffi-dev:i386
+    runs-on: ubuntu-22.04 # use 22.04 to get libffi-dev:i386
     steps:
     - uses: actions/checkout@v5
     - name: Install packages