promise/check_error_on_apache_log: Be tolerant with first partial line

   As we don't read entire file, the regex can eventually get
   garbage on the latest line to parse. This commit make it tolerant
   while check.

slapos/promise/check_error_on_apache_log/__init__.py

@@ -11,6 +11,7 @@ def test(log_file, maximum_delay):
   no_route_error = 0
   network_is_unreacheable = 0
   timeout = 0
+  parsing_failure = 0
   with open(log_file) as f:
 
     f.seek(0, 2)
@@ -23,11 +24,21 @@ def test(log_file, maximum_delay):
       if m is None:
         continue
       dt, level, msg = m.groups()
+      try:
         try:
           t = time.strptime(dt[1:-1], "%a %b %d %H:%M:%S %Y")
         except ValueError:
           # Fail to parser for the first time, try a different output.
           t = time.strptime(dt[1:-1], "%a %b %d %H:%M:%S.%f %Y")
+      except ValueError:
+          # Probably it fail to parse
+          if parsing_failure < 3:
+            # Accept failure 2 times, as the line can be actually
+            # cut on the middle.
+            parsing_failure += 1
+            continue
+          raise
+
       if maximum_delay and (time.time()-time.mktime(t)) > maximum_delay:
         # no result in the latest hour
         break
@@ -50,7 +61,6 @@ def test(log_file, maximum_delay):
 
   return "OK"
 
-
 def main():
   parser = argparse.ArgumentParser()
   parser.add_argument("-l", "--log-file", required=True)