exc.py: str_(): Fixed bug where UnicodeEncodeError would be raised when msg contains non-ASCII chars, by wrapping e.args⁰ in strings.ustr()

exc.py: print_ex(): Wrap msg in strings.to_unicode() to try to avoid UnicodeEncodeError when msg contains non-ASCII chars

sql.py: create_table(): Don't set pkey.nullable to False because the caller should make sure the pkey has the appropriate type

csv2db: Use sql_gen.TypedCol.nullable instead of manually adding 'NOT NULL' to the type. Ensure that pkeys are properly NOT NULL.

csv2db: Adding indexes: Create plain indexes using ensure_not_null=False because the indexes will primarily be used by the user to search for specific values, rather than by the mapping script which uses the ensure_not_null

sql.py: DbConn.col_info(): Run query with log_level=4 because it gathers information about database structure, and should have the same log_level as other queries that do that

csv2db: Adding indexes: Fixed bug where col.to_Col() could not be used because sql.add_index() does not support name-only columns (plain strings are OK, though)

sql.py: create_table(): has_pkey: Use new TypedCol.constraints to store 'PRIMARY KEY'

sql_gen.py: TypedCol: Added constraints instance var

sql_gen.py: EnsureNotNull: Made coalesce() all uppercase to match how pg_dump spells it