Schemata excluded from dbt docs generate with Redshift

[nydnarb]

Describe the bug

In Redshift, the following query is run during dbt docs generate:

    with late_binding as (
      select
        'rover'::varchar as table_database,
        table_schema,
        table_name,
        'LATE BINDING VIEW'::varchar as table_type,
        null::text as table_comment,

        column_name,
        column_index,
        column_type,
        null::text as column_comment
      from pg_get_late_binding_view_cols()
        cols(table_schema name, table_name name, column_name name,
             column_type varchar,
             column_index int)
        order by "column_index"
    ),

    table_owners as (

        select
            'rover'::varchar as table_database,
            schemaname as table_schema,
            tablename as table_name,
            tableowner as table_owner

        from pg_tables

        union all

        select
            'rover'::varchar as table_database,
            schemaname as table_schema,
            viewname as table_name,
            viewowner as table_owner

        from pg_views

    ),

    tables as (

      select
        table_catalog as table_database,
        table_schema,
        table_name,
        table_type

      from information_schema.tables

    ),

    table_columns as (

        select
            'rover'::varchar as table_database,
            table_schema,
            table_name,
            null::varchar as table_comment,

            column_name,
            ordinal_position as column_index,
            data_type as column_type,
            null::varchar as column_comment


        from information_schema."columns"

    ),

    unioned as (

        select *
        from tables
        join table_columns using (table_database, table_schema, table_name)

        union all

        select *
        from late_binding

    )

    select *,
        table_database || '.' || table_schema || '.' || table_name as table_id

    from unioned
    join table_owners using (table_database, table_schema, table_name)

    where table_schema != 'information_schema'
      and table_schema not like 'pg_%'

    order by "column_index"

This query is intended to ignore schemata that begin with pg_. However, in Redshift, an underscore _ represents any single character when using the like operator. I discovered this because we have a schema called pganalytics and docs were not generated for it. I think the fix is as simple as escaping the underscore as described here: https://docs.aws.amazon.com/redshift/latest/dg/r_patternmatching_condition_like.html

System information

Which database are you using dbt with?

• postgres
• redshift
• bigquery
• snowflake
• other (specify: ____________)

The output of dbt --version:

pipey-dbt (master) $ dbt --version
installed version: 0.14.3
   latest version: 0.15.0

Your version of dbt is out of date! You can find instructions for upgrading here:
https://docs.getdbt.com/docs/installation

The operating system you're using:
MacOS

The output of python --version:
Python 3.7.3