Update generate command to expect latest changes to data file format

There's now results that indicate errors in addition to the regular good
results. This updates generate so it actually parses the lines into
Result* structures and therefore can easily ignore the ones that have a
ResultError* type.

sbws/commands/generate.py

 from sbws.globals import (fail_hard, is_initted)
+from sbws.lib.resultdump import Result
+from sbws.lib.resultdump import ResultError
+from sbws.lib.resultdump import ResultSuccess
 from argparse import ArgumentDefaultsHelpFormatter
 from statistics import median
 import os
@@ -12,10 +15,14 @@ def read_result_file(fname, starting_dict=None):
     with open(fname, 'rt') as fd:
         for line in fd:
             d = json.loads(line)
+            res = Result.from_dict(d)
+            if isinstance(res, ResultError):
+                continue
+            assert isinstance(res, ResultSuccess)
             fp = d['fingerprint']
             if fp not in data:
                 data[fp] = []
-            data[fp].append(d)
+            data[fp].append(res)
     return data
 
 
@@ -37,11 +44,14 @@ class V3BWLine:
 def result_data_to_v3bw_line(data, fingerprint):
     assert fingerprint in data
     results = data[fingerprint]
-    nick = results[0]['nickname']
+    for res in results:
+        assert isinstance(res, ResultSuccess)
+    results = data[fingerprint]
+    nick = results[0].nickname
     speeds = [dl['amount'] / dl['duration']
-              for r in results for dl in r['downloads']]
+              for r in results for dl in r.downloads]
     speed = median(speeds)
-    rtts = [rtt for r in results for rtt in r['rtts']]
+    rtts = [rtt for r in results for rtt in r.rtts]
     return V3BWLine(fingerprint, speed, nick, rtts)