I am taking classes right not to get my PA Real Estate license. Any restrictive covenant that would prohibit the sale of the property on the basis of race, sex, religion or national origin would be illegal. Period. Even if you are not doing a VA or FHA loan, and taking a private mortgage any lender would negate the sale if a restrictive covenant (on who can buy the property) is present. Lenders, inorder to deal with banking/lending regulations cannot be a party to any deal that violates the Federal Fair Housing Act. Any homeowner that tried to honor such a covenant would be wide open to damages brought by any discriminated against buyer. Any real estate licensee who participated in such a deal would lose his/her license and the broker who held their license would also be fined/censured. It is that serious of an offense.
In practice, if upon listing a property such a restrictive covenenant is found, it is be pointed out that it is absolutely illegal (in some states, that would be redacted out of the paperwork as to not generate even a hint of discriminatory actions).
In fact, you should insist that the illegal clause be stricken from the paperwork -- if for no other reason than that it might be used to embarass you later.