Combine dependency clauses with the same root

[zanieb]

e.g. instead of "you require a and you require b" we should say "you require a and b"

Originally posted by @charliermarsh in #982 (comment)

[ibraheemdev]

#3225 does this for requirement errors, but we might be able to do this for more types of errors. e.g. "because foo is unavailable and bar is unavailable" could become "because foo and bar are unavailable" (#3225 (comment)).

[konstin]

Closing as a special case of #1901