trace: error messages shouldn't end with punctuation
trace: error messages shouldn't end with punctuation

Change-Id: I16a20ee2af6524a01b5d269023dc662053c7b66d
Reviewed-on: https://code-review.googlesource.com/11073
Reviewed-by: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>

googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go