Fix the libvirt tests

Signed-off-by: Pedro Algarvio <palgarvio@vmware.com>

tests/pytests/integration/modules/test_virt.py

@@ -2,6 +2,7 @@
 Validate the virt module
 """
 import logging
+import sys
 from numbers import Number
 from xml.etree import ElementTree
 
@@ -16,11 +17,34 @@ log = logging.getLogger(__name__)
 
 pytestmark = [
     pytest.mark.slow_test,
+    pytest.mark.skip_unless_on_linux,
     pytest.mark.skip_if_binaries_missing("docker"),
 ]
 
 
 def _install_salt_dependencies(container):
+    ret = container.run("bash", "-c", "echo $SALT_PY_VERSION")
+    assert ret.returncode == 0
+    if not ret.stdout:
+        log.warning(
+            "The 'SALT_PY_VERSION' environment variable is not set on the container"
+        )
+        salt_py_version = 3
+        ret = container.run(
+            "python3",
+            "-c",
+            "import sys; sys.stderr.write('{}.{}'.format(*sys.version_info))",
+        )
+        assert ret.returncode == 0
+        if not ret.stdout:
+            requirements_py_version = "py{}.{}".format(*sys.version_info)
+        else:
+            requirements_py_version = ret.stdout.strip()
+    else:
+        salt_py_version = requirements_py_version = ret.stdout.strip()
+
+    container.python_executable = f"python{salt_py_version}"
+
     dependencies = []
     for package, version in salt.version.dependency_information():
         if package not in ("packaging", "looseversion"):
@@ -29,8 +53,16 @@ def _install_salt_dependencies(container):
             continue
         dependencies.append(f"{package}=={version}")
     if dependencies:
-        ret = container.run("python3", "-m", "pip", "install", *dependencies)
+        ret = container.run(
+            container.python_executable,
+            "-m",
+            "pip",
+            "install",
+            f"--constraint=/salt/requirements/static/ci/py{requirements_py_version}/linux.txt",
+            *dependencies,
+        )
         log.debug("Install missing dependecies ret: %s", ret)
+        assert ret.returncode == 0
 
 
 @pytest.fixture(scope="module")