configure: Look for auxiliary Python installations
At the moment, we look for just "python3" and "python", which is good
enough almost all of the time. But ... if you are on a platform that
uses an older Python by default and only offers a newer Python as an
option, you'll have to specify --python=/usr/bin/foo every time.
We can be kind and instead make a cursory attempt to locate a suitable
Python binary ourselves, looking for the remaining well-known binaries.
This configure loop will prefer, in order:
1. Whatever is specified in $PYTHON
2. python3
3. python
4. python3.11 down through python3.6
Notes:
- Python virtual environment provides binaries for "python3", "python",
and whichever version you used to create the venv,
e.g. "python3.8". If configure is invoked from inside of a venv, this
configure loop will not "break out" of that venv unless that venv is
created using an explicitly non-suitable version of Python that we
cannot use.
- In the event that no suitable python is found, the first python found
is the version used to generate the human-readable error message.
- The error message isn't printed right away to allow later
configuration code to pick up an explicitly configured python.
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/configure b/configure
index a191246..0e41c5e 100755
--- a/configure
+++ b/configure
@@ -592,20 +592,43 @@
: ${make=${MAKE-make}}
-# We prefer python 3.x. A bare 'python' is traditionally
-# python 2.x, but some distros have it as python 3.x, so
-# we check that too
-python=
-explicit_python=no
-for binary in "${PYTHON-python3}" python
-do
- if has "$binary"
- then
- python=$(command -v "$binary")
- break
- fi
-done
+check_py_version() {
+ # We require python >= 3.6.
+ # NB: a True python conditional creates a non-zero return code (Failure)
+ "$1" -c 'import sys; sys.exit(sys.version_info < (3,6))'
+}
+
+python=
+first_python=
+if test -z "${PYTHON}"; then
+ explicit_python=no
+ # A bare 'python' is traditionally python 2.x, but some distros
+ # have it as python 3.x, so check in both places.
+ for binary in python3 python python3.11 python3.10 python3.9 python3.8 python3.7 python3.6; do
+ if has "$binary"; then
+ python=$(command -v "$binary")
+ if check_py_version "$python"; then
+ # This one is good.
+ first_python=
+ break
+ else
+ first_python=$python
+ fi
+ fi
+ done
+else
+ # Same as above, but only check the environment variable.
+ has "${PYTHON}" || error_exit "The PYTHON environment variable does not point to an executable"
+ python=$(command -v "$PYTHON")
+ explicit_python=yes
+ if check_py_version "$python"; then
+ # This one is good.
+ first_python=
+ else
+ first_python=$first_python
+ fi
+fi
# Check for ancillary tools used in testing
genisoimage=
@@ -1030,16 +1053,22 @@
if test -z "$python"
then
- error_exit "Python not found. Use --python=/path/to/python"
+ # If first_python is set, there was a binary somewhere even though
+ # it was not suitable. Use it for the error message.
+ if test -n "$first_python"; then
+ error_exit "Cannot use '$first_python', Python >= 3.6 is required." \
+ "Use --python=/path/to/python to specify a supported Python."
+ else
+ error_exit "Python not found. Use --python=/path/to/python"
+ fi
fi
+
if ! has "$make"
then
error_exit "GNU make ($make) not found"
fi
-# Note that if the Python conditional here evaluates True we will exit
-# with status 1 which is a shell 'false' value.
-if ! $python -c 'import sys; sys.exit(sys.version_info < (3,6))'; then
+if ! check_py_version "$python"; then
error_exit "Cannot use '$python', Python >= 3.6 is required." \
"Use --python=/path/to/python to specify a supported Python."
fi
