Fix inport errors and maintain compatibility with python 3.5x)

package_manager/__init__.py

@@ -250,7 +250,7 @@ class PACKAGE_OT_install(SubprocMixin, bpy.types.Operator):
 
     def _subproc_success(self, success: subproc.Success):
         self.report({'INFO'}, 'Package installed successfully')
-        getattr(bpy.ops, __package__).refresh_packages()
+        bpy.ops.package.refresh_packages()
         self.quit()
 
     def _subproc_aborted(self, aborted: subproc.Aborted):
@@ -311,7 +311,7 @@ class PACKAGE_OT_uninstall(SubprocMixin, bpy.types.Operator):
 
     def _subproc_success(self, success: subproc.Success):
         self.report({'INFO'}, 'Package uninstalled successfully')
-        getattr(bpy.ops, __package__).refresh_packages()
+        bpy.ops.package.refresh_packages()
         self.quit()
 
     def report_process_died(self):
@@ -446,7 +446,7 @@ class PACKAGE_OT_refresh(bpy.types.Operator):
     bl_description = "Check for new and updated packages"
 
     def execute(self, context):
-        getattr(bpy.ops, __package__).refresh_repositories()
+        bpy.ops.package.refresh_repositories()
         # getattr(bpy.ops, __package__).refresh_packages()
         return {'FINISHED'}
 
@@ -791,7 +791,7 @@ class WM_OT_package_toggle_expand(bpy.types.Operator):
 
 
 class PackageManagerPreferences(bpy.types.AddonPreferences):
-    bl_idname = __package__
+    bl_idname = 'package'
 
     package_url = bpy.props.StringProperty(
         name='Package URL',