This release contains major performance improvements for Spack environments, as

well as some bugfixes and minor changes.

* allow missing modules if they are blacklisted (#13540)

* speed up environment activation (#13557)

* mirror path works for unknown versions (#13626)

* environments: don't try to modify run-env if a spec is not installed (#13589)

* use semicolons instead of newlines in module/python command (#13904)

* verify.py: os.path.exists exception handling (#13656)

* Document use of the maintainers field (#13479)

* bugfix with config caching (#13755)

* hwloc: added 'master' version pointing at the HEAD of the master branch (#13734)

* config option to allow gpg warning suppression (#13744)

* fix for relative symlinks when relocating binary packages (#13727)

* allow binary relocation of strings in relative binaries (#13724)

This is a bugfix release on top of `v0.13.0`. Specific fixes include:

* `spack find` now displays variants and other spec constraints

* bugfix: uninstall should find concrete specs by DAG hash (#13598)

* environments: make shell modifications partially unconditional (#13523)

* binary distribution: relocate text files properly in relative binaries (#13578)

* bugfix: fetch prefers to fetch local mirrors over remote resources (#13545)

* environments: only write when necessary (#13546)

* bugfix: spack.util.url.join() now handles absolute paths correctly (#13488)

* sbang: use utf-8 for encoding when patching (#13490)

* Specs with quoted flags containing spaces are parsed correctly (#13521)

* targets: print a warning message before downgrading (#13513)

* Travis CI: Test Python 3.8 (#13347)

* Documentation: Database.query methods share docstrings (#13515)

* cuda: fix conflict statements for x86-64 targets (#13472)

* cpu: fix clang flags for generic x86_64 (#13491)

* syaml_int type should use int.__repr__ rather than str.__repr__ (#13487)

* elpa: prefer 2016.05.004 until sse/avx/avx2 issues are resolved (#13530)

* trilinos: temporarily constrain netcdf@:4.7.1 (#13526)