output more descriptive output when dependencies fail

owrx/__main__.py

@@ -89,12 +89,17 @@ Support and info:       https://groups.io/g/openwebrx
     coreConfig = CoreConfig()
 
     featureDetector = FeatureDetector()
-    if not featureDetector.is_available("core"):
+    failed = featureDetector.get_failed_requirements("core")
+    if failed:
         logger.error(
             "you are missing required dependencies to run openwebrx. "
-            "please check that the following core requirements are installed and up to date:"
+            "please check that the following core requirements are installed and up to date: %s",
+            ", ".join(failed)
         )
-        logger.error(", ".join(featureDetector.get_requirements("core")))
+        for f in failed:
+            description = featureDetector.get_requirement_description(f)
+            if description:
+                logger.error("description for %s:\n%s", f, description)
         return
 
     # Get error messages about unknown / unavailable features as soon as possible

owrx/feature.py

@@ -110,6 +110,9 @@ class FeatureDetector(object):
     def is_available(self, feature):
         return self.has_requirements(self.get_requirements(feature))
 
+    def get_failed_requirements(self, feature):
+        return [req for req in self.get_requirements(feature) if not self.has_requirement(req)]
+
     def get_requirements(self, feature):
         try:
             return FeatureDetector.features[feature]