Some error message improvements

index bcadc27..cb89d88 100644
@@ -43,7 +43,7 @@ except ImportError:
     logger.info("Importing cPickle failed. "
                 "Falling back to a very slow implementation.")
 
-__cache_version__ = "141"
+__cache_version__ = "142"
 
 def getCacheFile(path, filename):
     return os.path.join(path, filename)

@@ -99,6 +99,7 @@ class CoreRecipeInfo(RecipeInfoCommon):
 
         self.skipreason = self.getvar('__SKIPPED', metadata)
         if self.skipreason:
+            self.pn = self.getvar('PN', metadata) or bb.parse.BBHandler.vars_from_file(filename,metadata)[0]
             self.skipped = True
             self.provides  = self.depvar('PROVIDES', metadata)
             self.rprovides = self.depvar('RPROVIDES', metadata)

index 7cf43a0..efcbf1b 100644
@@ -59,11 +59,13 @@ class state:
 
 class SkippedPackage:
     def __init__(self, info = None, reason = None):
+        self.pn = None
         self.skipreason = None
         self.provides = None
         self.rprovides = None
 
         if info:
+            self.pn = info.pn
             self.skipreason = info.skipreason
             self.provides = info.provides
             self.rprovides = info.rprovides

@@ -313,7 +315,7 @@ class BBCooker:
         bb.data.expandKeys(localdata)
         # We set abort to False here to prevent unbuildable targets raising
         # an exception when we're just generating data
-        taskdata = bb.taskdata.TaskData(False)
+        taskdata = bb.taskdata.TaskData(False, skiplist=self.skiplist)
 
         runlist = []
         for k in pkgs_to_build:

@@ -1038,7 +1040,7 @@ class BBCooker:
         bb.data.update_data(localdata)
         bb.data.expandKeys(localdata)
 
-        taskdata = bb.taskdata.TaskData(self.configuration.abort)
+        taskdata = bb.taskdata.TaskData(self.configuration.abort, skiplist=self.skiplist)
 
         runlist = []
         for k in targets:

index 93c04ba..9dd7b66 100644
@@ -287,11 +287,12 @@ class BuildCompleted(BuildBase):
 class NoProvider(Event):
     """No Provider for an Event"""
 
-    def __init__(self, item, runtime=False, dependees=None):
+    def __init__(self, item, runtime=False, dependees=None, reasons=[]):
         Event.__init__(self)
         self._item = item
         self._runtime = runtime
         self._dependees = dependees
+        self._reasons = reasons
 
     def getItem(self):
         return self._item

index 81a42b7..e857f9a 100644
@@ -41,7 +41,7 @@ class TaskData:
     """
     BitBake Task Data implementation
     """
-    def __init__(self, abort = True, tryaltconfigs = False):
+    def __init__(self, abort = True, tryaltconfigs = False, skiplist = None):
         self.build_names_index = []
         self.run_names_index = []
         self.fn_index = []

@@ -70,6 +70,8 @@ class TaskData:
         self.abort = abort
         self.tryaltconfigs = tryaltconfigs
 
+        self.skiplist = skiplist
+
     def getbuild_id(self, name):
         """
         Return an ID number for the build target name.

@@ -348,6 +350,22 @@ class TaskData:
                 dependees.append(self.fn_index[fnid])
         return dependees
 
+    def get_reasons(self, item, runtime=False):
+        """
+        Get the reason(s) for an item not being provided, if any
+        """
+        reasons = []
+        if self.skiplist:
+            for fn in self.skiplist:
+                skipitem = self.skiplist[fn]
+                if skipitem.pn == item:
+                    reasons.append("%s was skipped: %s" % (skipitem.pn, skipitem.skipreason))
+                elif runtime and item in skipitem.rprovides:
+                    reasons.append("%s RPROVIDES %s but was skipped: %s" % (skipitem.pn, item, skipitem.skipreason))
+                elif not runtime and item in skipitem.provides:
+                    reasons.append("%s PROVIDES %s but was skipped: %s" % (skipitem.pn, item, skipitem.skipreason))
+        return reasons
+
     def add_provider(self, cfgData, dataCache, item):
         try:
             self.add_provider_internal(cfgData, dataCache, item)

@@ -369,7 +387,7 @@ class TaskData:
             return
 
         if not item in dataCache.providers:
-            bb.event.fire(bb.event.NoProvider(item, dependees=self.get_rdependees_str(item)), cfgData)
+            bb.event.fire(bb.event.NoProvider(item, dependees=self.get_rdependees_str(item), reasons=self.get_reasons(item)), cfgData)
             raise bb.providers.NoProvider(item)
 
         if self.have_build_target(item):

@@ -381,7 +399,7 @@ class TaskData:
         eligible = [p for p in eligible if not self.getfn_id(p) in self.failed_fnids]
 
         if not eligible:
-            bb.event.fire(bb.event.NoProvider(item, dependees=self.get_dependees_str(item)), cfgData)
+            bb.event.fire(bb.event.NoProvider(item, dependees=self.get_dependees_str(item), reasons=["No eligible PROVIDERs exist for '%s'" % item]), cfgData)
             raise bb.providers.NoProvider(item)
 
         if len(eligible) > 1 and foundUnique == False:

@@ -418,14 +436,14 @@ class TaskData:
         all_p = bb.providers.getRuntimeProviders(dataCache, item)
 
         if not all_p:
-            bb.event.fire(bb.event.NoProvider(item, runtime=True, dependees=self.get_rdependees_str(item)), cfgData)
+            bb.event.fire(bb.event.NoProvider(item, runtime=True, dependees=self.get_rdependees_str(item), reasons=self.get_reasons(item, True)), cfgData)
             raise bb.providers.NoRProvider(item)
 
         eligible, numberPreferred = bb.providers.filterProvidersRunTime(all_p, item, cfgData, dataCache)
         eligible = [p for p in eligible if not self.getfn_id(p) in self.failed_fnids]
 
         if not eligible:
-            bb.event.fire(bb.event.NoProvider(item, runtime=True, dependees=self.get_rdependees_str(item)), cfgData)
+            bb.event.fire(bb.event.NoProvider(item, runtime=True, dependees=self.get_rdependees_str(item), reasons=["No eligible RPROVIDERs exist for '%s'" % item]), cfgData)
             raise bb.providers.NoRProvider(item)
 
         if len(eligible) > 1 and numberPreferred == 0:

index a4deb46..b7abdf8 100644
@@ -208,6 +208,9 @@ def main(server, eventHandler):
                     logger.error("Nothing %sPROVIDES '%s' (but %s %sDEPENDS on or otherwise requires it)", r, event._item, ", ".join(event._dependees), r)
                 else:
                     logger.error("Nothing %sPROVIDES '%s'", r, event._item)
+                if event._reasons:
+                    for reason in event._reasons:
+                        logger.error("%s", reason)
                 continue
 
             if isinstance(event, bb.runqueue.runQueueTaskStarted):

index e857f9a..79602b6 100644
@@ -387,7 +387,7 @@ class TaskData:
             return
 
         if not item in dataCache.providers:
-            bb.event.fire(bb.event.NoProvider(item, dependees=self.get_rdependees_str(item), reasons=self.get_reasons(item)), cfgData)
+            bb.event.fire(bb.event.NoProvider(item, dependees=self.get_dependees_str(item), reasons=self.get_reasons(item)), cfgData)
             raise bb.providers.NoProvider(item)
 
         if self.have_build_target(item):

index edd54d0..22104f1 100644
@@ -124,6 +124,18 @@ def findPreferredProvider(pn, cfgData, dataCache, pkg_pn = None, item = None):
             itemstr = " (for item %s)" % item
         if preferred_file is None:
             logger.info("preferred version %s of %s not available%s", pv_str, pn, itemstr)
+            available_vers = []
+            for file_set in pkg_pn:
+                for f in file_set:
+                    pe, pv, pr = dataCache.pkg_pepvpr[f]
+                    ver_str = pv
+                    if pe:
+                        ver_str = "%s:%s" % (pe, ver_str)
+                    if not ver_str in available_vers:
+                        available_vers.append(ver_str)
+            if available_vers:
+                available_vers.sort()
+                logger.info("versions of %s available: %s", pn, ' '.join(available_vers))
         else:
             logger.debug(1, "selecting %s as PREFERRED_VERSION %s of package %s%s", preferred_file, pv_str, pn, itemstr)