Update s3_to_exasol to python3

[mjohannfunke]

I noticed that the s3_to_exasol script still uses Python 2, which is generally discontinued in 2020 and will be discontinued by exasol in the next major release. I updated the code to Python 3 and their respective packages. As far as I can tell this now provides the same functionality, it lists all keys in a given bucket (using the ContinuationToken logic of boto3).

Since I am handling json files right now, I cannot test the remaining parts of the script (importing csvs).

[allipatev]

Hi @mjohannfunke, thanks for your contribution! Let us take a look. I was also thinking of leaving out the "force_http" input parameter as it doesn't seem applicable to boto3.

[mjohannfunke]

Hey @allipatev , you are right with the force_http parameter, I removed it. I also looked through the whole script to see where it was used and removed those spots as far as I can tell.