fix issue spesmilo#103 check open files limit during initialization

Prevent database corruption due to default open file limits.
If limit is too low, print an error message and exit.

run_electrum_server

@@ -25,6 +25,7 @@ import threading
 import json
 import os
 import imp
+import resource
 
 
 if os.path.dirname(os.path.realpath(__file__)) == os.getcwd():
@@ -49,6 +50,12 @@ if os.getuid() == 0:
     print "Run the install script to create a non-privileged user."
     sys.exit()
 
+# prevent database corruption due to default open file limits
+softlimit, hardlimit = resource.getrlimit(resource.RLIMIT_OFILE)
+if hardlimit < 64000:
+    print "Warning: Your open files limit is too low." 
+    sys.exit()
+
 def attempt_read_config(config, filename):
     try:
         with open(filename, 'r') as f: