* Tighten up graphviz package
The fun started when configure discovered a broken/partial
installation of `swig` in `/usr/local`, then auto-discovered my
system's python and ruby packages.
- SpackException doesn't seem to exist. Convert it to a SpackError
and call `.format(...)` on the error string to fill in the
placeholder.
- Pull swig out of the list of languages. It's something that can be
asked for explicitly and that is needed if *any* of the langagues
are enabled. It's disabled by default.
- Explicitly disable the languages that are in "untested_bindings"
list lest the configure script pick up things from the system.
* Touch up variant description string
* Clean up conditional statement
* Use InstallError, not SpackError
* Drop the swig variant
Get rid of the swig variant and drive that bit based on whether any
languages are enabled.
* Move perl to the untested list
That's not strictly accurate. I tested it and it doesn't work.
There's a missing depends_on(). When you add that you'll discover
that the language binding bit can't find Perl's 'EXTERN.h'. Then
you'll discover that graphviz's `configure` script doesn't have a good
way to include the paths to Perl's bits (looks like I'll have to
gather them for each language and then use them to build `CFLAGS` and
`CXXFLAGS` and `LDFLAGS`). While pondering that, you'll discover that
EXTERN.h is buried down here:
```
opt/spack/linux-centos7-x86_64/gcc-4.8.5/perl-5.24.1-35ejv4426dmzreum4ekdibu3ddmhquvi/lib/5.24.1/x86_64-linux/CORE/EXTERN.h
```
and decide that you wish you had never thought to actually test
`graphviz+perl`.
I could find that directory with a snippet like so:
```
perl -MConfig -e 'print "$Config{archlib}\n"'
```
but at this point I'm much, much further down this rabbit hole then I
ever wanted to go.
* Convince python that tested_bindings is a list
When I removed `+perl` and made `tested_bindings` a list of one
thing, I ended up with this:
```
==> Error: cannot concatenate 'str' and 'tuple' objects
```
* Flake8 cleanup
* Don't convert a string to a string
* rm unused () and clarify variable name
Feedback from @adamjstewart
- Get rid of some unnecessary parens.
- Clearer variable name and use.
* Further cleanup of language enabling loop
Now we don't need that pesky temporary variable.
bfb45ba1ce