Django (django-ses-gateway) gives default region as EU-WEST-1 instead of US-EAST-1
Finally, got the solution.
'django_ses_gateway' (version 0.1.1) module of python has a bug.
By default, it selects EU-WEST-1 region, 
hence,  'sending_mail.py' file requires correction to not to hard-cord a region of EU.
The location of installed package can be found using 'pip3 show django-ses-gateway' command
I am having application on EC2 that requires to send an email.
I am using Django with AWS, and module of 'django-ses-gateway' to send an email.
EC2 is configured, hence on ~/.aws folder I am having appropriate credentials file with region as 'default'
However, whenever application tries to send an email by default it is trying to use  "EU-WEST-1" region which is not expected one, as it should use "US-EAST-1".
Because of wrong region, application fails.
PS:
I also verified that "settings.py" file is not overwriting region,