Relative paths not correctly appended to XDG_DATA_DIRS lists with entries that lack '/' at the end #100
Description
'/' is appended only to the last entry of XDG_DATA_DIRS if missing, not the rest of the entries.
Steps to reproduce:
XDG_DATA_DIRS=path1:path2 XDG_DATA_HOME=path3 flyby
-> Tries to look for TLEs in path1flyby/tles rather than path1/flyby/tles.
