stream-clone: remove unused code in test-clone-stream.t We are not using the extension we create inline, we are using `tests/testlib/ext-stream-clone-steps.py`. So let us deleted the unused version.

stream-clone: document the ext-stream-clone-steps.py utility extension This extension is useful, let us clarify how to use it.

test-treemanifest: cleanup the test to more easily show server side error This made my life easier debugging.

test: make test-contrib-perf.t more robust Some code path are far too fast now. We raise de number to make sure the run keep to that floor.

safehasattr: pass attribute name as string instead of bytes This is a step toward replacing `util.safehasattr` usage with plain `hasattr`. The builtin function behave poorly in Python2 but this was fixed in Python3. These change are done one by one as they tend to have a small odd to trigger puzzling breackage.

safehasattr: pass attribute name as string instead of bytes This is a step toward replacing `util.safehasattr` usage with plain `hasattr`. The builtin function behave poorly in Python2 but this was fixed in Python3. These change are done one by one as they tend to have a small odd to trigger puzzling breackage.

safehasattr: pass attribute name as string instead of bytes This is a step toward replacing `util.safehasattr` usage with plain `hasattr`. The builtin function behave poorly in Python2 but this was fixed in Python3. These change are done one by one as they tend to have a small odd to trigger puzzling breackage.

safehasattr: pass attribute name as string instead of bytes This is a step toward replacing `util.safehasattr` usage with plain `hasattr`. The builtin function behave poorly in Python2 but this was fixed in Python3. These change are done one by one as they tend to have a small odd to trigger puzzling breackage.

safehasattr: pass attribute name as string instead of bytes This is a step toward replacing `util.safehasattr` usage with plain `hasattr`. The builtin function behave poorly in Python2 but this was fixed in Python3. These change are done one by one as they tend to have a small odd to trigger puzzling breackage.

safehasattr: pass attribute name as string instead of bytes This is a step toward replacing `util.safehasattr` usage with plain `hasattr`. The builtin function behave poorly in Python2 but this was fixed in Python3. These change are done one by one as they tend to have a small odd to trigger puzzling breackage.