Install multiple pythons on CircleCI

.circleci/images/install-python.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+# vim:fileencoding=utf-8
+# License: GPLv3 Copyright: 2019, Kovid Goyal <kovid at kovidgoyal.net>
+
+import io
+import os
+import shlex
+import shutil
+import subprocess
+import sys
+import tarfile
+from urllib.request import urlopen
+
+PY, URL = sys.argv[1], sys.argv[2]
+SRC = f'/usr/src/{PY}'
+
+os.chdir('/usr/src')
+before = frozenset(os.listdir('.'))
+
+
+def run(cmd):
+    cmd = shlex.split(cmd)
+    p = subprocess.Popen(cmd)
+    if p.wait() != 0:
+        raise SystemExit(p.returncode)
+
+
+with urlopen(URL) as f:
+    data = f.read()
+
+with tarfile.open(fileobj=io.BytesIO(data), mode='r:xz') as tf:
+    tf.extractall()
+after = frozenset(os.listdir('.'))
+src_dir = tuple(after - before)[0]
+os.rename(src_dir, SRC)
+os.chdir(SRC)
+run(f'./configure --prefix=/opt/{PY} --enable-shared --with-system-expat --with-system-ffi --without-ensurepip')
+run(f'make -j {os.cpu_count()}')
+run('make install')
+os.chdir('/')
+shutil.rmtree(SRC)