Depression definitely can make it hard to find the motivation for exercise (among other things) because loss of interest in normal activities, along with the ability to enjoy them, is often one of the main symptoms of depression. But what does that mean in practical terms?
It definitely doesn't mean that you'll have to wait until your depression has cleared up before you'll be able to start building up a regular exercise routine. In fact, it probably means just the opposite. You might need to stop looking for your motivation or waiting for it to appear before you start working out. Instead, recognize that feeling unmotivated is part of the illness and that starting a regular exercise routine is an important part of the cure. It's a lot like getting out of bed in the morning on a low day—you might not feel like it; but you know that if you don't do it, things are only going to go downhill from there.