Debug reg.cgi - how to know the exception detail in try..except

Question

after digging more into the app i have found that when i run the http://192.168.0.110/cgi/reg.cgi?&username=shaun&identity=3
It returns false... which means that the reg.cgi could insert the username and identity inside sqlite db.. my problem is how will i know what error is coming as i dont have working knowledge of cgi script.. below is the code
How to print the type of error in except like in dotnet we have try...catch(Exception ex){ ex.messsage} where ex.message will tell me the error.. how to do this in cgi
print 'Content-type: text/plain\n\n<?xml version="1.0" encoding="utf-8"?>\n<result>'
if user:
    try:
        c = db.cursor()
        c.execute("insert or replace into registrations values (?, ?, datetime('now'))", (user, identity))
        print '\t<update>true</update>'
    except:
        print '\t<update>false</update>'
for f in friends:
    print "\t<friend>\n\t\t<user>%s</user>" % (xml.sax.saxutils.escape(f), )
    c = db.cursor()
    c.execute("select m_username, m_identity from registrations where m_username = ? and m_updatetime > datetime('now', '-1 hour')", (f, ))
    for result in c.fetchall():
        eachIdent = result[1]
        if not eachIdent:
            eachIdent = ""
        print "\t\t<identity>%s</identity>" % (xml.sax.saxutils.escape(eachIdent), )
        if f != result[0]:
            print "\t\t<registered>%s</registered>" % (xml.sax.saxutils.escape(result[0]), )
    print "\t</friend>"
db.commit()
print "</result>"

Answer 1

try:
  db_cursor.execute('some hopefully valid SQL;')
except sqlite3.Error, msg:
  print msg
After adding the above code i recieved an error : unable to open the database.. so after some googling
i found the below answer http://jaux.net/2008/12/18/sqlite3-unable-to-open-database-file/
Also Having being pissed for a while, I finally figured out what was wrong  here: The web server needs the write permission to not only the database  file, but also the containing directory of that file.