init: better error reporting on failed components

vcsserver/http_main.py

@@ -58,23 +58,30 b' from vcsserver.exceptions import HTTPRep'
 from vcsserver.lib.exc_tracking import store_exception
 from vcsserver.server import VcsServer
 
+
+git_import_err = None
 try:
     from vcsserver.git import GitFactory, GitRemote
-except ImportError:
+except ImportError as e:
     GitFactory = None
     GitRemote = None
+    git_import_err = e
 
+hg_import_err = None
 try:
     from vcsserver.hg import MercurialFactory, HgRemote
-except ImportError:
+except ImportError as e:
     MercurialFactory = None
     HgRemote = None
+    hg_import_err = e
 
+svn_import_err = None
 try:
     from vcsserver.svn import SubversionFactory, SvnRemote
-except ImportError:
+except ImportError as e:
     SubversionFactory = None
     SvnRemote = None
+    svn_import_err = e
 
 
 def _is_request_chunked(environ):
@@ -126,13 +133,13 b' class VCS(object):'
             git_factory = GitFactory()
             self._git_remote = GitRemote(git_factory)
         else:
-            log.info("Git client import failed")
+            log.error("Git client import failed: %s", git_import_err)
 
         if MercurialFactory and HgRemote:
             hg_factory = MercurialFactory()
             self._hg_remote = HgRemote(hg_factory)
         else:
-            log.info("Mercurial client import failed")
+            log.error("Mercurial client import failed: %s", hg_import_err)
 
         if SubversionFactory and SvnRemote:
             svn_factory = SubversionFactory()
@@ -141,7 +148,7 b' class VCS(object):'
             hg_factory = MercurialFactory()
             self._svn_remote = SvnRemote(svn_factory, hg_factory=hg_factory)
         else:
-            log.info("Subversion client import failed")
+            log.error("Subversion client import failed: %s", svn_import_err)
 
         self._vcsserver = VcsServer()
 
@@ -149,8 +156,7 b' class VCS(object):'
         if self.locale:
             log.info('Settings locale: `LC_ALL` to %s', self.locale)
         else:
-            log.info(
-                'Configuring locale subsystem based on environment variables')
+            log.info('Configuring locale subsystem based on environment variables')
         try:
             # If self.locale is the empty string, then the locale
             # module will use the environment variables. See the
@@ -162,8 +168,7 b' class VCS(object):'
                 'Locale set to language code "%s" with encoding "%s".',
                 language_code, encoding)
         except locale.Error:
-            log.exception(
-                'Cannot set locale, not configuring the locale system')
+            log.exception('Cannot set locale, not configuring the locale system')
 
 
 class WsgiProxy(object):