PyPi builds missing subpackages
**Impact of the bug**
WMCore in general

**Describe the bug**
As reported in this post:
https://github.com/dmwm/WMCore/issues/10407#issuecomment-1346589360

MSTransferor `2.1.5`, based on the PyPi package, is actually missing some of the subpackages.

The real problem seem to be on the definition of recursive packages or not (usage of `+` in the setup_dependencies.py module).

**How to reproduce it**
Either inspecting the package from PyPi, or interactively building it with `python setup.py clean sdist`.

**Expected behavior**
All the required packages, as defined in:
https://github.com/dmwm/WMCore/blob/master/setup_dependencies.py

should be part of the final package uploaded to PyPi.
Apparently, the right change here should be done in the the setup_dependencies.py module, by defining when:
a) we only want to add a package; or
b) we want to add a package and all its subpackages.

**Additional context and error message**
None
diff --git a/setup_build.py b/setup_build.py
index 61611d484..dc69696e7 100644
--- a/setup_build.py
+++ b/setup_build.py
@@ -20,9 +20,11 @@ def walk_dep_tree(system):
     statics that the system depends on.
 
     system is a dict containing:
-        {'packages': ['Package'],
-         'systems':['foo'],
-         'statics': ['bar']}
+        {'bin': ['bin_script_A'],
+         'packages': ['package_name_A'],
+         'modules': ['module_name_A'],
+         'systems':['system_name_A'],
+         'statics': ['non_python_statics_A']}
     """
     packages = set()
     statics = set()
@@ -153,13 +155,12 @@ def things_to_build(command, pypi=False):
 
     # and the corresponding source directories and files
     package_src_dirs = []
-    module_src_files = []
     for package in dependency_tree['packages']:
         # Need to recurse packages
         recurse = package.endswith('+')
         print(package, recurse)
         package = package.rstrip('+')
-        src_path = '%s/src/python/%s' % (get_path_to_wmcore_root(), package.replace('.','/'))
+        src_path = '%s/src/python/%s' % (get_path_to_wmcore_root(), package.replace('.', '/'))
         package_src_dirs.extend(list_packages([src_path], recurse))
     return package_src_dirs, dependency_tree['modules']
 
diff --git a/setup_dependencies.py b/setup_dependencies.py
index 0f84691b2..475f151b2 100644
--- a/setup_dependencies.py
+++ b/setup_dependencies.py
@@ -1,8 +1,20 @@
 #!/usr/bin/env python
 """
-Manage dependancies by declaring systems here.
-A system can depend on packages or other systems.
-If a package ends with a + include all subpackages.
+This data structure is consumed by the setup_build.py script, in order to add
+the required packages to each of the WMCore systems.
+
+It contains the name of the systems that can be built out of the WMCore
+repository, and their list of dependencies, which can be:
+ * bin: list with the name of executable scripts available in the root bin/ area
+ * packages: list with the name of a WMCore python packages (i.e. a directory
+   containing an __init__.py file)
+     * note that if it's suffixed with the '+' sign, subpackages will also be
+     recursively searched and added to the final system
+ * modules: list with the name of specific modules (a .py file) to be added.
+ * statics: list with the name of files classified as statics, e.g. css, templates,
+   javascript, etc.
+ * systems: list with WMCore system aliases (i.e., like a meta-package that can
+   be used by multiple WMCore systems).
 """
 dependencies = {
     'wmc-rest': {
@@ -129,23 +141,23 @@ dependencies = {
         'statics': [],
     },
     'reqmgr2ms-unmerged': {
-        'packages': ['WMCore.MicroService.MSUnmerged'],
+        'packages': ['WMCore.MicroService.MSUnmerged+'],
         'systems': ['reqmgr2ms-core'],
     },
     'reqmgr2ms-output': {
-        'packages': ['WMCore.MicroService.MSOutput'],
+        'packages': ['WMCore.MicroService.MSOutput+'],
         'systems': ['reqmgr2ms-core'],
     },
     'reqmgr2ms-transferor': {
-        'packages': ['WMCore.MicroService.MSTransferor'],
+        'packages': ['WMCore.MicroService.MSTransferor+'],
         'systems': ['reqmgr2ms-core'],
     },
     'reqmgr2ms-monitor': {
-        'packages': ['WMCore.MicroService.MSMonitor'],
+        'packages': ['WMCore.MicroService.MSMonitor+'],
         'systems': ['reqmgr2ms-core'],
     },
     'reqmgr2ms-rulecleaner': {
-        'packages': ['WMCore.MicroService.MSRuleCleaner'],
+        'packages': ['WMCore.MicroService.MSRuleCleaner+'],
         'systems': ['reqmgr2ms-core'],
     },
     'global-workqueue': {
['setup_build.py', 'setup_dependencies.py']