Remove support for running with Python 2.7 (#33063)

* Remove CI jobs related to Python 2.7

* Remove Python 2.7 specific code from Spack core

* Remove externals for Python 2 only

* Remove llnl.util.compat

lib/spack/spack_installable/main.py

@@ -1,3 +1,7 @@
+# Copyright 2013-2022 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import os
 import sys
 from os.path import dirname as dn
@@ -14,10 +18,6 @@ def main(argv=None):
 
     # Add external libs
     spack_external_libs = os.path.join(spack_lib_path, "external")
-
-    if sys.version_info[:2] <= (2, 7):
-        sys.path.insert(0, os.path.join(spack_external_libs, "py2"))
-
     sys.path.insert(0, spack_external_libs)
     # Here we delete ruamel.yaml in case it has been already imported from site
     # (see #9206 for a broader description of the issue).
@@ -31,29 +31,6 @@ def main(argv=None):
     if "ruamel" in sys.modules:
         del sys.modules["ruamel"]
 
-    # The following code is here to avoid failures when updating
-    # the develop version, due to spurious argparse.pyc files remaining
-    # in the libs/spack/external directory, see:
-    # https://github.com/spack/spack/pull/25376
-    # TODO: Remove in v0.18.0 or later
-    try:
-        import argparse  # noqa: F401
-    except ImportError:
-        argparse_pyc = os.path.join(spack_external_libs, "argparse.pyc")
-        if not os.path.exists(argparse_pyc):
-            raise
-        try:
-            os.remove(argparse_pyc)
-            import argparse  # noqa: F401
-        except Exception:
-            msg = (
-                "The file\n\n\t{0}\n\nis corrupted and cannot be deleted by Spack. "
-                "Either delete it manually or ask some administrator to "
-                "delete it for you."
-            )
-            print(msg.format(argparse_pyc))
-            sys.exit(1)
-
     import spack.main  # noqa: E402
 
     sys.exit(spack.main.main(argv))