Correctly display errors in configure-pg-env.sh.

* Print errors in configure-pg-env.sh to STDERR instead of STDOUT.
* Don't run `export` in recreate-schema.sh until after
  configure-pg-env.sh is successfully ran, to avoid the case where
  it would run `export` without any arguments. `set -e` ensures it
  won't run the `export $ENV` line if configure-pg-env.sh fails.

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