Augustine, and other Christian leaders ignore scripture on this point. Isaiah 45:7 ("I form the light and create darkness; I make peace and create evil; I am the Lord that does all these things") and Deuteronomy 30:15-20 ("See, I have set before you this day life and good and death and evil . . . .therefore choose life that you may live, you and your seed; to love the Lord your God, to hearken to His voice, and to cleave unto Him; for that is your life and the length of your days. . . ."), both make it clear that good and evil were created by God. Moreover, the verses at Deuteronomy make it clear that the creation of evil went along with the gift of free will, without which we would be robots or hand puppets. Our task, Deuteronomy is telling us, is to "choose life" by knowing God through study, walking in His ways, following His commandments, and loving Him with full hearts.
The assumption that God only creates good, and not evil, does not come from the Hebrew Scriptures, but appears to demonstrate early influences to the Church by the dualistic views of Zoroastrianism and Manichaeism. The NT reflects this, too, by its exaggeration of the abilities and independence of Satan, in contrast to the Jewish view, as reflected in Job, for example (that Satan was a prosecutorial angel working at the direction of God).
The existence of both good and evil in the world are both essential to the concepts of free will, reward and punishment, and the spiritual and moral development of mankind. Therefore from God's perspective, the co-existence of good and evil in the world as options for Man serve a Divine purpose and therefore serve an ultimate good.
Augustine's position, really, is not from the Bible at all. Realize that Augustine was heavily influenced by Manichaeism. Manicheaeism was a Persian religion that, like Zoroastrianism and Gnosticism, had a dualistic cosmology where there were forces that were exclusiviely good opposed to forces that were exclusively evil. Widengren, Geo Mesopotamian elements in Manichaeism (King and Saviour II): Studies in Manichaean, Mandaean, and Syrian-gnostic religion, Lundequistska bokhandeln, 1946. Manichaeism was popular from the 3rd to 7th centuries in the Eastern Mediterranean area and was among Christianity's chief competitors. See Andrew Welburn, Mani, the Angel and the Column of Glory: An Anthology of Manichaean Texts (Edinburgh: Floris Books, 1998), p. 68. Augustine had been a Manichaean before converting to Christianity, his enthusiastic conversion coming shortly after Roman Emperor Theodosius I had issued a decree of death for any Manichaeians in 382 and shortly before he declared Christianity the empire's official religion. Some modern scholars have suggested that Manichaean ways of thinking influenced the development of some of Augustine's ideas, such as the nature of good and evil, the idea of hell, the separation of groups into elect, hearers, and sinners, and the hostility to the flesh and sexual activity. A. Adam, Das Fortwirken des Manichäismus bei Augustin. In: ZKG (69) 1958, S. 1–25 (cited in Wikipedia article on Manichaeism). As these views are contrary to views in the Hebrew Scriptures, it is more likely they were introduced by Augustine from Manichaeism. It could be argued that, like many Church innovations, these changes were made not only out of Augustine's personal beliefs, but to make Church doctrine more attractive in parts of the world where Zoroastrianism and Manichaeism held influence.