Commit 5bb989993 added some code for hiding/showing the cursor when
running on the terminal, but accidentally made it so that it always
printed the invisible control codes, even when not on a tty or when
--quiet was specified. This turns out to be surprisingly bad (e.g. it
breaks the official docker python builds). So, let's not do that.
Fixes gh-3418
One of the downsides of pip's new hiding of build chatter is that for
packages that take a very long time to build (e.g. scipy) the user gets
no indication that anything is happening for a very long time (e.g. tens
of minutes), and is likely to get frustrated and hit Control-C. This can
also create issues for automated systems that kill jobs that don't
produce occasional output (e.g. Travis-CI).
This commit implements an idea discussed here:
https://github.com/pypa/pip/issues/2732#issuecomment-153215371
where we put up a spinner that rotates whenever the underlying build
produces output. I tried it on scipy, and it the experience was quite
pleasant! It spun around, sometimes fast and sometimes slow, and then
there was one uncomfortable pause for ~1 minute while a very gnarly C++
file got compiled, but that's okay because it was actually providing
accurate feedback.
It looks like:
```
Running setup.py install for scipy ... /
Running setup.py install for scipy ... -
Running setup.py install for scipy ... \
Running setup.py install for scipy ... done
```
or if the command has non-zero return code, or an exception is raised,
you get:
```
Running setup.py install for scipy ... /
Running setup.py install for scipy ... -
Running setup.py install for scipy ... \
Running setup.py install for scipy ... error
```
* Use the colorama module to enable the "clear the line" ANSI escape
code on Windows.
* Disable cursor hiding on Windows since Windows terminal doesn't
support it nor does colorama.
