pluploader install --mpac-key seems to be broken

[Fabian Siegel]

pluploader:

2021-02-17 12:55:12 INFO Downloading app de.scandio.confluence.plugins.pocketquery (latest)...
2021-02-17 12:55:13 INFO Successfully downloaded app to /tmp/pluploader/736b1b26-03c0-4ff7-ab0b-4c322f9ad5f0
2021-02-17 12:55:13 INFO 736b1b26-03c0-4ff7-ab0b-4c322f9ad5f0 will be uploaded to http://localhost:8090
  0%|                                                                                                                                    | 0/100 [00:20<00:53,  1.85it/s]  0%|                                                                                                                                            | 0/100 [01:37<?, ?it/s]

confluence:

...
java.lang.IllegalArgumentException: The artifact URI file:/var/atlassian/application-data/confluence/plugins-cache/1613562914835plugin_7984101278552235241_736b1b26-03c0-4ff7-ab0b-4c322f9ad5f0 is not a valid plugin artifact
...

com.atlassian.upm.spi.PluginInstallException: Unknown error, plugin not installed