fix: datasource passed unicode to foreach_execute in py26 (#4232)

- when collecting in py26 env, if the foreach_execute specs depends
  on DatasourceProvider, the provider will be in unicode type and causes
  the followed validate() fail
- this change converted the unicode to string by force for all 'cmd' passed to
  CommandOutputProvider

Signed-off-by: Xiangce Liu <xiangceliu@redhat.com>

rh-pre-commit.version: 2.3.1
rh-pre-commit.check-secrets: ENABLED

insights/core/spec_factory.py

@@ -334,7 +334,7 @@ def __init__(self, cmd, ctx, root="insights_commands", save_as=None,
                  args=None, split=True, keep_rc=False, ds=None, timeout=None,
                  inherit_env=None, override_env=None, signum=None, cleaner=None):
         super(CommandOutputProvider, self).__init__()
-        self.cmd = cmd
+        self.cmd = cmd if six.PY3 else str(cmd)
         self.root = root
         self.save_as = save_as
         self.ctx = ctx