fix several printb usage with python3

The following three tools are recently changed to use
printb in order to flush out the result.
  opensnoop.py, tcpaccept.py, tcpconnect.py

With python3, however, these tools have errors like below:
  TypeError: %b requires a bytes-like object, or an object that implements __bytes__, not 'str'
  Traceback (most recent call last):
    File "_ctypes/callbacks.c", line 234, in 'calling callback function'
    File "/usr/lib/python3.6/site-packages/bcc/table.py", line 572, in raw_cb_
      callback(cpu, data, size)
    File "../../tools/opensnoop.py", line 248, in print_event
      printb(b'%s' % event.fname.decode('utf-8', 'replace'))

This patch fixed printb related issues for these three tools
for python3. The python2 still works with the fix.
Signed-off-by: Yonghong Song <yhs@fb.com>

tools/opensnoop.py

@@ -245,7 +245,7 @@ def print_event(cpu, data, size):
     if args.extended_fields:
         print("%08o " % event.flags, end="")
 
-    printb(b'%s' % event.fname.decode('utf-8', 'replace'))
+    printb(b'%s' % event.fname)
 
 # loop with callback to print_event
 b["events"].open_perf_buffer(print_event, page_cnt=64)

tools/tcpaccept.py

@@ -245,9 +245,10 @@ def print_ipv4_event(cpu, data, size):
             start_ts = event.ts_us
         print("%-9.3f" % ((float(event.ts_us) - start_ts) / 1000000), end="")
     printb(b"%-6d %-12.12s %-2d %-16s %-16s %-4d" % (event.pid,
-        event.task.decode('utf-8', 'replace'), event.ip,
-        inet_ntop(AF_INET, pack("I", event.daddr)),
-        inet_ntop(AF_INET, pack("I", event.saddr)), event.lport))
+        event.task, event.ip,
+        inet_ntop(AF_INET, pack("I", event.daddr)).encode(),
+        inet_ntop(AF_INET, pack("I", event.saddr)).encode(),
+        event.lport))
 
 def print_ipv6_event(cpu, data, size):
     event = ct.cast(data, ct.POINTER(Data_ipv6)).contents
@@ -257,8 +258,9 @@ def print_ipv6_event(cpu, data, size):
             start_ts = event.ts_us
         print("%-9.3f" % ((float(event.ts_us) - start_ts) / 1000000), end="")
     printb(b"%-6d %-12.12s %-2d %-16s %-16s %-4d" % (event.pid,
-        event.task.decode('utf-8', 'replace'), event.ip,
-        inet_ntop(AF_INET6, event.daddr),inet_ntop(AF_INET6, event.saddr),
+        event.task, event.ip,
+        inet_ntop(AF_INET6, event.daddr).encode(),
+        inet_ntop(AF_INET6, event.saddr).encode(),
         event.lport))
 
 # initialize BPF

tools/tcpconnect.py

@@ -225,9 +225,9 @@ def print_ipv4_event(cpu, data, size):
     if args.print_uid:
         print("%-6d" % event.uid, end="")
     printb(b"%-6d %-12.12s %-2d %-16s %-16s %-4d" % (event.pid,
-        event.task.decode('utf-8', 'replace'), event.ip,
-        inet_ntop(AF_INET, pack("I", event.saddr)),
-        inet_ntop(AF_INET, pack("I", event.daddr)), event.dport))
+        event.task, event.ip,
+        inet_ntop(AF_INET, pack("I", event.saddr)).encode(),
+        inet_ntop(AF_INET, pack("I", event.daddr)).encode(), event.dport))
 
 def print_ipv6_event(cpu, data, size):
     event = ct.cast(data, ct.POINTER(Data_ipv6)).contents
@@ -239,8 +239,8 @@ def print_ipv6_event(cpu, data, size):
     if args.print_uid:
         print("%-6d" % event.uid, end="")
     printb(b"%-6d %-12.12s %-2d %-16s %-16s %-4d" % (event.pid,
-        event.task.decode('utf-8', 'replace'), event.ip,
-        inet_ntop(AF_INET6, event.saddr), inet_ntop(AF_INET6, event.daddr),
+        event.task, event.ip,
+        inet_ntop(AF_INET6, event.saddr).encode(), inet_ntop(AF_INET6, event.daddr).encode(),
         event.dport))
 
 # initialize BPF