Replace assert.Fail with assert.FailNow (#27578)

assert.Fail() will continue to execute the code while assert.FailNow()
not. I thought those uses of assert.Fail() should exit immediately.
PS: perhaps it's a good idea to use
[require](https://pkg.go.dev/github.com/stretchr/testify/require)
somewhere because the assert package's default behavior does not exit
when an error occurs, which makes it difficult to find the root error
reason.

tests/integration/api_packages_conan_test.go

@@ -296,7 +296,7 @@ func TestPackageConan(t *testing.T) {
 
 						assert.Equal(t, int64(len(contentConaninfo)), pb.Size)
 					} else {
-						assert.Fail(t, "unknown file: %s", pf.Name)
+						assert.FailNow(t, "unknown file: %s", pf.Name)
 					}
 				}
 			})