Installed MercurialEclispe, and had the following problem when trying to clone a repo:
failed to import extension mercurial_keyring
There are a number of solutions, such as installing the keyring module on the system’s python. However that gets you into a load of problems if you dont have the correct MSVC installed.
By far the easiest solution is to install TortoiseHG, and point the hg binary to C:\Program Files\TortoiseHg\hg.exe in the MecurialEclipse plugin preferences.