openSUSE package query and install enhancements

[gleichdick]

Enable pip installer, use rpm capabilities for package lookup to prevent package renaming issues.

For example, in python.yml the python-numpy dependency is resolved to the opensuse rpm package python-numpy which is absent. But the package python2-numpy provides it as a capability as shown below:

$ rpm -q --provides python2-numpy
python-numpy = 1.16.5
python2-numpy = 1.16.5-2.1
python2-numpy(x86-64) = 1.16.5-2.1

So instead of matching the exact package name at dependency resolving the capabilities should be queried (--whatprovides flag).

$ rpm -q --whatprovides python2-numpy
python2-numpy-1.16.5-2.1.x86_64
$ rpm -q --whatprovides python-numpy
python2-numpy-1.16.5-2.1.x86_64

Of course, if none of the installed package provides the given capability the return code is still non-zero:

$ rpm -q --whatprovides anyunknowncap; echo $?
no package provides anyunknowncap
1

[nuclearsandwich]

It looks like the rpm facilities for the redhat platform are a bit more sophisticated. Is it worth centralizing and sharing some of this logic or is there too much divergence between them? Also asking @cottsay as my local RedHat expert and probable contributor for the redhat RPM handling.

[cottsay]

This is a similar approach to the one taken in the RedHat installer:

rosdep/src/rosdep2/platforms/redhat.py

Lines 110 to 118 in cfa21c8

	cmd = ['rpm', '-q', '--whatprovides', '--qf', '[%{PROVIDES}\n]']
	cmd.extend(packages)
	std_out = exec_fn(cmd)
	out_lines = std_out.split('\n')
	for index, package in enumerate(packages):
	if package in out_lines:
	ret_list.append(raw_packages[index])
	return ret_list

Invoking the rpm executable repetitively on a large workspace was pretty slow, so a single command is invoked for all of the packages and the output is parsed to ensure availability since the return value isn't useful anymore.

This change, however, shouldn't make the openSUSE installer any less performant than it currently is, and uses an already proven approach.

[cottsay]

Is it worth centralizing and sharing some of this logic...?

Maybe. The RedHat installer tries to use the RPM python module if it is available, so I think we'd need to do some testing to ensure it works right, but I expect that the RPM solution in redhat.py would work here as-is.

I don't think that work should block this PR though.

[cottsay]

I haven't actually tried the change myself, by it makes sense.