fix: python agent: install on Debian python >= 3.10

Starting with Debian's Python 3.10, the default install scheme is
'posix_local' which is a Debian specific scheme based on 'posix_prefix'
but with an added 'local' prefix. This is the default so users doing
system wide manual installations of python modules end up in
'/usr/local'. This interferes with our autotools based install which
already defaults to '/usr/local' and expect a provided prefix to be used
verbatim.

Monkeypatch sysconfig to override this scheme and use 'posix_prefix' instead.

Change-Id: I08fe77b6c8807515765e3ad0344aa6849e573b90
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/python-lttngust/setup.py.in b/python-lttngust/setup.py.in
index 24f8d6738bb821933a8086f72e2a47246c6b6723..13c88af8e1695f6f7e28c7616e183477417dc984 100644 (file)
--- a/python-lttngust/setup.py.in
+++ b/python-lttngust/setup.py.in
@@ -23,6 +23,28 @@ if sys.version_info < (3, 12):
 else:
     from setuptools import setup, Extension
 
+# Starting with Debian's Python 3.10, the default install scheme is
+# 'posix_local' which is a Debian specific scheme based on 'posix_prefix' but
+# with an added 'local' prefix. This is the default so users doing system wide
+# manual installations of python modules end up in '/usr/local'. This
+# interferes with our autotools based install which already defaults to
+# '/usr/local' and expect a provided prefix to be used verbatim.
+#
+# Monkeypatch sysconfig to override this scheme and use 'posix_prefix' instead.
+if sys.version_info >= (3, 10):
+    import sysconfig
+
+    original_get_preferred_scheme = sysconfig.get_preferred_scheme
+
+    def our_get_preferred_scheme(key):
+        scheme = original_get_preferred_scheme(key)
+        if scheme == "posix_local":
+            return "posix_prefix"
+        else:
+            return scheme
+
+    sysconfig.get_preferred_scheme = our_get_preferred_scheme
+
 PY_PATH_WARN_MSG = """
 -------------------------------------WARNING------------------------------------
 The install directory used:\n ({0})\nis not included in your PYTHONPATH.