Flush HINT line screen prompt

[gaow]

For docker based steps we do pull from the web the docker image every time we run them. The problem is that with the prompt below:

INFO: Running 5: Indel re-alignment
HINT: Pulling docker image gaow/gatk3:2.0

one cannot tell if it is running the step or still having troubles pulling the docker images. For example currently this above command is hanging. It would be nice to be able to tell. I think simply removing that HINT after docker images is pulled would be good enough: clear the current line and move the cursor back to the beginning after docker pull is complete.

[BoPeng]

Ideally it should be something like

Pulling docker image gaow/gatk3:2.0 ...

then after a while

Pulling docker image gaow/gatk3:2.0 ...... done.

but this is difficult to implement, especially when this line could be sent to cells of SoS Notebook.

[gaow]

I see, I guess the complication is sending that line to SoS Notebook ... where you typically implement a spinning wheel or something like that? In the command shell just removing that line is good enough to me.