Are you trying to install Lightroom CC 2015 on your computer for the first time, or do you already have it installed and are trying to update it to the 2015.0.1 version?
Here is more information about Error 49:
Hi mf, 'update failed. Please try again (49) this message only shows you because you could not Properly download Adobe Photoshop Lightroom. So in this action my suggestion is again properly download Lightroom and set up again. Thank you.
Right, and if you have any further problems then you can use the direct links instead...