fix: Properly fail init() when missing an extractor

* This allow workaround for the missing TDB

ArchiveExtractor/Access.py

@@ -45,25 +45,43 @@ def init(
 
     ae._Extractors = (None, None)
     ae._AttrTables = (None, None)
+    _Extr = []
+    _Attr = []
 
     try:
         logger.setLevel(getattr(logging, loglevel.upper()))
     except AttributeError:
         logger.error("Wrong log level specified: {}".format(loglevel.upper()))
+        return
 
     logger.debug("Instanciating extractors device proxy...")
 
-    ae._Extractors = (tango.DeviceProxy(HdbExtractorPath), tango.DeviceProxy(TdbExtractorPath))
-    logger.debug("{} and {} instanciated.".format(*ae._Extractors))
+    for p in [HdbExtractorPath, TdbExtractorPath]:
+        try:
+            _Extr.append(tango.DeviceProxy(p))
+        except tango.DevFailed:
+            logger.error("Could not find extractor {}".format(p))
+            return
+
+    logger.debug("{} and {} instanciated.".format(*_Extr))
 
     logger.debug("Configuring extractors device proxy...")
-    for e in ae._Extractors:
+    for e in _Extr:
         # set timeout to 3 sec
         e.set_timeout_millis(3000)
 
     logger.debug("Filling attributes lookup tables...")
-    ae._AttrTables = tuple(e.getattnameall() for e in ae._Extractors)
-    logger.debug("HDB: {} TDB: {} attributes counted".format(len(ae._AttrTables[0]), len(ae._AttrTables[1])))
+    for e in _Extr:
+        try:
+            _Attr.append(e.getattnameall())
+        except AttributeError:
+            logger.error("Could not fetch attributes for extractor {}".format(e))
+            return
+
+    logger.debug("HDB: {} TDB: {} attributes counted".format(len(_Attr[0]), len(_Attr[1])))
+
+    ae._Extractors = tuple(_Extr)
+    ae._AttrTables = tuple(_Attr)
 
 ##########################################################################
 ###                    Module access functions                         ###