Not pushing when there are empty md5 clauses in any DVC-file

[adrianohrl]

Instead of using the dvc run command, I manually created a DVC-file to compose my processo pipeline as its last stage. For minimizing my efforts, I cleaned all md5 clauses presented in this DVC-file. Before reproducing it, I ran the dvc push command, leading to an issue. I could not push properly until I removed all empty md5 clauses from this DVC-file.

DVC version: 0.83.0
Platform: Ubuntu 18.04
Method of installation: apt install dvc[s3]

[efiop]

For the record: The issue happens if you replace md5: 123456 with md5: in any dvc-file and then try to dvc push or dvc status -c it.

Discord context: https://discordapp.com/channels/485586884165107732/485596304961962003/679431956777402368

[pared]

Error message fixed in #3365

[pared]

@adrianohrl now when trying to push you should see suggestion how lack of md5's can be fixed.