Repository: spack/spack

Issue:
spack find : always prompt 0 installed packages
On a clean `develop` checkout : 

```
$ git clone https://github.com/LLNL/spack.git
Cloning into 'spack'...
remote: Counting objects: 25613, done.
remote: Compressing objects: 100% (42/42), done.
remote: Total 25613 (delta 12), reused 3 (delta 3), pack-reused 25557
Receiving objects: 100% (25613/25613), 6.65 MiB | 6.46 MiB/s, done.
Resolving deltas: 100% (13031/13031), done.
Checking connectivity... done.

$ cd spack
$ . share/spack/setup-env.sh 
$ spack compilers
==> Available compilers
-- gcc ----------------------------------------------------------
gcc@4.8

$ spack install zlib
==> Installing zlib
==> Trying to fetch from file:///home/mculpo/production/spack-mirror/zlib/zlib-1.2.8.tar.gz
######################################################################## 100,0%
==> Staging archive: /home/mculpo/tmp/spack/var/spack/stage/zlib-1.2.8-d6pdl6xvnvap6ihrqcqtgvweghbszmix/zlib-1.2.8.tar.gz
==> Created stage in /home/mculpo/tmp/spack/var/spack/stage/zlib-1.2.8-d6pdl6xvnvap6ihrqcqtgvweghbszmix
==> No patches needed for zlib
==> Building zlib
==> Successfully installed zlib
  Fetch: 0.01s.  Build: 3.69s.  Total: 3.70s.
[+] /home/mculpo/tmp/spack/opt/spack/linux-x86_64/gcc-4.8/zlib-1.2.8-d6pdl6xvnvap6ihrqcqtgvweghbszmix

$ spack find
==> 0 installed packages.

$ spack install szip
==> Installing szip
==> Trying to fetch from file:///home/mculpo/production/spack-mirror/szip/szip-2.1.tar.gz
######################################################################## 100,0%
==> Staging archive: /home/mculpo/tmp/spack/var/spack/stage/szip-2.1-esfmhl54wbdb7nnnip6y6jbxlbmxs2jq/szip-2.1.tar.gz
==> Created stage in /home/mculpo/tmp/spack/var/spack/stage/szip-2.1-esfmhl54wbdb7nnnip6y6jbxlbmxs2jq
==> No patches needed for szip
==> Building szip
==> Successfully installed szip
  Fetch: 0.01s.  Build: 8.09s.  Total: 8.10s.
[+] /home/mculpo/tmp/spack/opt/spack/linux-x86_64/gcc-4.8/szip-2.1-esfmhl54wbdb7nnnip6y6jbxlbmxs2jq

$ spack find 
==> 0 installed packages.
```

The db seems to be written correctly : 

```
database:
  installs:
    d6pdl6xvnvap6ihrqcqtgvweghbszmix:
      explicit: true
      installed: true
      path: /home/mculpo/tmp/spack/opt/spack/linux-x86_64/gcc-4.8/zlib-1.2.8-d6pdl6xvnvap6ihrqcqtgvweghbszmix
      ref_count: 0
      spec:
        zlib:
          arch: linux-x86_64
          compiler:
            name: gcc
            version: '4.8'
          dependencies: {}
          namespace: builtin
          parameters:
            cflags: []
            cppflags: []
            cxxflags: []
            fflags: []
            ldflags: []
            ldlibs: []
          version: 1.2.8
    esfmhl54wbdb7nnnip6y6jbxlbmxs2jq:
      explicit: true
      installed: true
      path: /home/mculpo/tmp/spack/opt/spack/linux-x86_64/gcc-4.8/szip-2.1-esfmhl54wbdb7nnnip6y6jbxlbmxs2jq
      ref_count: 0
      spec:
        szip:
          arch: linux-x86_64
          compiler:
            name: gcc
            version: '4.8'
          dependencies: {}
          namespace: builtin
          parameters:
            cflags: []
            cppflags: []
            cxxflags: []
            fflags: []
            ldflags: []
            ldlibs: []
          version: '2.1'
  version: 0.9.1
```



Discussion:

Resolving patch:
diff --git a/var/spack/repos/builtin/packages/prank/package.py b/var/spack/repos/builtin/packages/prank/package.py
--- a/var/spack/repos/builtin/packages/prank/package.py
+++ b/var/spack/repos/builtin/packages/prank/package.py
@@ -36,6 +36,7 @@ class Prank(Package):
     depends_on('mafft')
     depends_on('exonerate')
     depends_on('bpp-suite')      # for bppancestor
+    conflicts('%gcc@7.2.0', when='@:150803')
 
     def install(self, spec, prefix):
         with working_dir('src'):


Test patch: