Add a warning on Python 2.7 deprecation (#33052)

Co-authored-by: alalazo <alalazo@users.noreply.github.com>
Co-authored-by: Todd Gamblin <tgamblin@llnl.gov>

lib/spack/spack/main.py

@@ -547,6 +547,12 @@ def setup_main_options(args):
     # Assign a custom function to show warnings
     warnings.showwarning = send_warning_to_tty
 
+    if sys.version_info[:2] == (2, 7):
+        warnings.warn(
+            "Python 2.7 support is deprecated and will be removed in Spack v0.20.\n"
+            "    Please move to Python 3.6 or higher."
+        )
+
     # Set up environment based on args.
     tty.set_verbose(args.verbose)
     tty.set_debug(args.debug)

lib/spack/spack/test/cmd/commands.py

@@ -22,6 +22,9 @@
 spack.main.add_all_commands(parser)
 
 
+@pytest.mark.skipif(
+    sys.version_info[:2] == (2, 7), reason="Fails as the output contains a warning on Python 2.7"
+)
 def test_names():
     """Test default output of spack commands."""
     out1 = commands().strip().split("\n")