How to get output from gdb.execute in PythonGDB (GDB 7.1)?

So is there a way to receive the output of an gdb.execute in GDB 7.1?

No.

Your best bet is to arrange for GDB-7.3 to be available. Since GDB doesn't usually use shared libraries (beyond libc and perhaps libpython), you can just copy gdb binary with your script. That will be much easier and more maintainable solution than the alternative you proposed.

You can write to a file, then read the file, for example:

os.system("rm tmp.txt")
gdb.execute("set logging file tmp.txt")
gdb.execute("set logging on")
mainsec=gdb.execute("info proc mappings")
gdb.execute("set logging off")
mainsec = open("tmp.txt").read()

The old version of gdb.execute was far superior though.

FYI now (tested with gdb 8.1) you can use the to_string parameter

https://sourceware.org/gdb/onlinedocs/gdb/Basic-Python.html

gdb.execute (command [, from_tty [, to_string]])

By default, any output produced by command is sent to GDB’s standard output (and to the log output if logging is turned on). If the to_string parameter is True, then output will be collected by gdb.execute and returned as a string. The default is False, in which case the return value is None.