pgsql: pg_upgrade: Improve error messages

pg_upgrade: Improve error messages

Make wording more accurate and add strerror() information.

Discussion: /messages/by-id/24c8bd05-aed1-6301-919d-8acbabdb8c24@2ndquadrant.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/cd917ffb9a43e9e4699c2a89d495ee02a8701034

Modified Files
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src/bin/pg_upgrade/exec.c | 4 ++--
src/bin/pg_upgrade/option.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)