Question: Why is this definite integral note evaluating?

int((1-r^3+3*r^2-3*r)(r^3-3*r^2+3*r), r = 0 .. 1);
print(`output redirected...`); # input placeholder
/ 3 2
| / 3 2 \ / 3 2 \
int\-r\r - 3 r + 3 r/ + 3 r\r - 3 r + 3 r/

\
/ 3 2 \ |
- 3 r\r - 3 r + 3 r/ + 1, r = 0 .. 1/

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