Compatibility with Blender 2.93 / Python 3.9 → require Blender 2.80+

The code now requires Python 3.7 or newer, as a side-effect of the changes
required for compatibility with 3.9 (as used in Blender 2.93). As a result,
Blender Cloud Add-on now requires Blender 2.80 or newer.

blender_cloud/__init__.py

@@ -25,7 +25,7 @@ bl_info = {
     'blender': (2, 80, 0),
     'location': 'Addon Preferences panel, and Ctrl+Shift+Alt+A anywhere for texture browser',
     'description': 'Texture library browser and Blender Sync. Requires the Blender ID addon '
-                   'and Blender 2.77a or newer.',
+                   'and Blender 2.80 or newer.',
     'wiki_url': 'https://wiki.blender.org/index.php/Extensions:2.6/Py/'
                 'Scripts/System/BlenderCloud',
     'category': 'System',

blender_cloud/async_loop.py

@@ -43,6 +43,8 @@ def setup_asyncio_executor():
         # On Windows, the default event loop is SelectorEventLoop, which does
         # not support subprocesses. ProactorEventLoop should be used instead.
         # Source: https://docs.python.org/3/library/asyncio-subprocess.html
+        #
+        # NOTE: this is  actually the default even loop in Python 3.9+.
         loop = asyncio.ProactorEventLoop()
         asyncio.set_event_loop(loop)
     else:
@@ -73,7 +75,11 @@ def kick_async_loop(*args) -> bool:
         log.warning('loop closed, stopping immediately.')
         return True
 
-    all_tasks = asyncio.Task.all_tasks()
+    # Passing an explicit loop is required. Without it, the function uses
+    # asyncio.get_running_loop(), which raises a RuntimeError as the current
+    # loop isn't running.
+    all_tasks = asyncio.all_tasks(loop=loop)
+
     if not len(all_tasks):
         log.debug('no more scheduled tasks, stopping after this kick.')
         stop_after_this_kick = True