Python FileNotFoundError despite clearly having found the file

I'm working on a mailbomb program that randomizes images from a given directory. The code looks like this:

import schedule, time, smtplib, random, os, sys, socket
from email.mime.text import MIMEText
from email.mime.image import MIMEImage
from email.mime.application import MIMEApplication
from email.mime.multipart import MIMEMultipart

# Image randomization still under development

def message(subject="Python Notification",
            text="", img="", attachment=None):

    msg = MIMEMultipart()
    msg['Subject'] = subject
    msg.attach(MIMEText(text))

    if type(img) is not list:
        img=[img]
    for one_img in img:
        path = "C:\\Users\\JoeBiden\\Desktop\\PJ\\AMP\\ImgLib"
        files=os.listdir(path)
        randPic=random.choice(files)
        img_data = open(randPic, 'rb').read()
        msg.attach(MIMEImage(img_data,
                             name=os.path.basename(img_data)))

    if attachment is not None:
        if type(attachment) is not list:
            attachment = [attachment]
        for one_attachment in attachment:
            with open(one_attachment, 'rb') as f:
                file = MimeApplication(
                    f.read(),
                    name=os.path.basename(one_attachment)
                )
            file['Content-Disposition'] = f'attachment;\
            filename="{os.path.basename(one_attachment)}"'
            msg-attach(file)
    return msg

def mail():

    smtp=smtplib.SMTP('smtp.gmail.com', 587)
    smtp.ehlo()
    smtp.starttls()
    smtp.login('umomghaey@gmail.com', 'PEEENIS')
    msg = message("Pizza", "Pizza", r"C:\Users\JoeBiden\Desktop\PJ\AMP\ImgLib")
    to = ("cheeseburger@gmail.com")
    smtp.sendmail(from_addr="beesechurger@gmail.com",
                  to_addrs=to, msg=msg.as_string())
    smtp.quit()


schedule.every(2).seconds.do(mail)

while True:
    schedule.run_pending()
    time.sleep(1)

When running in CMD I get the following error:

        ret = self.job_func()
  File "C:\Users\JoeBiden\Desktop\PJ\AMP\MailRandomizer.py", line 46, in mail
    msg = message("Pizza", "Pizza", r"C:\Users\JoeBiden\Desktop\PJ\AMP\ImgLib")
  File "C:\Users\JoeBiden\Desktop\PJ\AMP\MailRandomizer.py", line 22, in message
    img_data = open(randPic, 'rb').read()
FileNotFoundError: [Errno 2] No such file or directory: 'RandImageFile.jpg'

To me the error seems paradoxical since it clearly shows me that it has found one of the desired files in the correct directory. That being the 'RandImageFile.jpg'

os.listdir() only gives you the filenames, so try replacing

files=os.listdir(path)

with something like

files = [os.path.join(path, f) for f in os.listdir(path)]