Add a link to a virtualenv guide
Add a link to a virtualenv guide


Former-commit-id: 76af553c6580c950265af8e159246b82c29df4df [formerly b631013a4c02b28fa258598d0aa26b9636fa98bd]
Former-commit-id: d13e00963475259adc28120d643d7a76d96c1c1c
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine