That is just arbitrary text that is sent from the server; the client just displays what the server sends. Note that every line is prefixed with remote. It is usually used for error messages, or just some informational text about the server.
In this case, it appears to be the Atlassian Logo, as Atlassian is the company that owns Bitbucket. Based on another question, it looks like this is intended to be colored using ANSI escape sequences as a rainbow, likely to celebrate today's Supreme Court's decision to strike down laws against gay marriage in the US. It may be the case that your terminal is not interpreting those escape sequences, and so you are just seeing the monochrome logo, rather than the rainbow.
