check_software: only check shared parts that are used in software

check_software was checking all shared parts, which was an easy
implementation but turned out to be problematic, both when running on
test nodes because if one software installs broken shared parts all
softwares being tested afterwards were failing and also during
development because we needed to prune broken shared parts when
fixing problems reported by check_software.

This inspects buildout's .installed.cfg to guess which shared parts
are used.

slapos/testing/check_software.py

@@ -34,6 +34,7 @@ import warnings
 
 import pkg_resources
 import requests
+from six.moves.configparser import ConfigParser
 
 try:
   import subprocess32 as subprocess
@@ -209,14 +210,24 @@ def checkSoftware(slap, software_url):
                         **locals()))
     return executable_link_error_list
 
-  paths_to_check = (
-      os.path.join(slap.software_directory, software_hash),
-      slap.shared_directory,
-  )
+  software_directory = os.path.join(slap.software_directory, software_hash)
+  paths_to_check = set((software_directory, ))
+
+  # Compute the paths to check by inspecting buildout installed database
+  # for this software. We are looking for shared parts installed by recipes.
+  config_parser = ConfigParser()
+  config_parser.read(os.path.join(software_directory, '.installed.cfg'))
+  for section_name in config_parser.sections():
+    for option_name in 'location', '__buildout_installed__':
+      if config_parser.has_option(section_name, option_name):
+         for section_path in config_parser.get(section_name, option_name).splitlines():
+           if section_path and not section_path.startswith(software_directory):
+             paths_to_check.add(section_path)
+
   error_list.extend(
       checkExecutableLink(
           paths_to_check,
-          paths_to_check + tuple(slap._shared_part_list),
+          tuple(paths_to_check) + tuple(slap._shared_part_list),
       ))
 
   # check this software is not referenced in any shared parts.