There should be no single quotes here 'A''some value'.
Either use double quotes to preserve the upper case spelling of "A":
CREATE TABLE "A" ...
Or don't use quotes at all:
CREATE TABLE A ...
which is identical to
CREATE TABLE a ...
because all unquoted identifiers are folded to lower case automatically in PostgreSQL.
You could avoid problems with the index name completely by using simpler syntax:
CREATE TABLE csd_relationship (
csd_relationship_id serial PRIMARY KEY,
type_id integer NOT NULL,
object_id integer NOT NULL
);
Does the same as your original query, only it avoids naming conflicts automatically. It picks the next free identifier automatically. More about the serial type in the manual.