Fail to install gitlab on ubuntu

Now I am trying to install gitlab for ubuntu that be hosted on a virtual machine. Its version is 15.10 and it is 64-bit. I try to install it following this tutorial. But I got such error:

Reading package lists... DoneBuilding dependency tree       Reading state information... DoneE: Unable to locate package gitlab-ce

The content of /etc/apt/sources.list.d/gitlab_gitlab-ce.list is :

# this file was generated by packages.gitlab.com for# the repository at https://packages.gitlab.com/gitlab/gitlab-cedeb https://packages.gitlab.com/gitlab/gitlab-ce/ubuntu/ wily maindeb-src https://packages.gitlab.com/gitlab/gitlab-ce/ubuntu/ wily main

Do you know how can I fix this issue? Thanks a lot in advance!

EDIT:

After I installed a ubuntu with version of 16.04, the previous error does not exist anymore. But now a new one occurs :( When I run apt-get install gitlab-ce, I got the error of no avaliable space. I ran df -Th and here is the output

Filesystem     Type      Size  Used Avail Use% Mounted onudev           devtmpfs  2.6G     0  2.6G   0% /devtmpfs          tmpfs     524M  7.7M  516M   2% /run/dev/sda1      ext4      4.6G  4.1G  245M  95% /tmpfs          tmpfs     2.6G   21M  2.6G   1% /dev/shmtmpfs          tmpfs     5.0M  4.0K  5.0M   1% /run/locktmpfs          tmpfs     2.6G     0  2.6G   0% /sys/fs/cgrouptmpfs          tmpfs     524M   56K  524M   1% /run/user/1000

So there are some partitions that I can utilize. Do you know how to install the gitlab to those available partitions?