Add get_package_list as a required method for pkgman

var/ramble/repos/builtin.mock/package_managers/info/package_manager.py

@@ -137,6 +137,10 @@ def _after_make_experiments(self, workspace, app_inst=None):
 
     package_manager_family("info-package-manager")
 
+    def get_package_list(self, workspace):
+        del workspace
+        return []
+
     def environment_load_commands(self) -> List[str]:
         return []
 

var/ramble/repos/builtin.mock/package_managers/when-package-manager/package_manager.py

@@ -65,6 +65,10 @@ class WhenPackageManager(PackageManagerBase):
         when=["+pkg_man_required_key"],
     )
 
+    def get_package_list(self, workspace):
+        del workspace
+        return []
+
     def environment_load_commands(self) -> List[str]:
         return []
 

var/ramble/repos/builtin/base_classes/package-manager-base/base_class.py

@@ -240,10 +240,10 @@ def _add_software_to_results(self, workspace, app_inst=None):
             prov_cache[self.name][env_name] = pkg_list
         self.app_inst.result.software[self.output_prefix] = pkg_list
 
+    # Methods that need to be defined by every derived package manager
+    @abc.abstractmethod
     def get_package_list(self, workspace):
         """Method used by add_software_to_results phase to get software provenance info"""
-        del workspace
-        return []
 
     @abc.abstractmethod
     def environment_load_commands(self) -> List[str]: