Fixup tplist and argdist for python3 compat

sys.exc_value and sys.exc_type should come from sys.exc_info()

Convert (decode) char* return values from C functions to a native python
str.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>

src/python/bcc/__init__.py

@@ -446,7 +446,7 @@ class BPF(object):
 
     @staticmethod
     def find_library(libname):
-        return lib.bcc_procutils_which_so(libname)
+        return lib.bcc_procutils_which_so(libname.encode("ascii")).decode()
 
     def attach_uprobe(self, name="", sym="", addr=None,
             fn_name="", pid=-1, cpu=0, group_fd=-1):

tools/argdist.py

@@ -673,8 +673,8 @@ struct __string_t { char s[%d]; };
                 except:
                         if self.args.verbose:
                                 traceback.print_exc()
-                        elif sys.exc_type is not SystemExit:
-                                print(sys.exc_value)
+                        elif sys.exc_info()[0] is not SystemExit:
+                                print(sys.exc_info()[1])
                 self._close_probes()
 
 if __name__ == "__main__":

tools/tplist.py

@@ -86,6 +86,6 @@ if __name__ == "__main__":
                 else:
                         print_tracepoints()
         except:
-                if sys.exc_type is not SystemExit:
-                        print(sys.exc_value)
+                if sys.exc_info()[0] is not SystemExit:
+                        print(sys.exc_info()[1])