Force jsonschema dependency to be <3.0.0.
Force jsonschema dependency to be <3.0.0.

One of the real dependencies of fusesoc relies on jsonschema >= 2.5.1. Unfortunately, as of this commit date allows alpha 2 of jsonschema 3.0.0 to be selected which fails to package correctly in the python 3.5 environment. This commit forces jsonschema < 3.0.0 as a workaround.

Perhaps this needs revisiting?

olofk/fusesoc,lowRISC/fusesoc,olofk/fusesoc,lowRISC/fusesoc