[Snyk] Fix for 4 vulnerabilities

[snyk-bot]

Snyk has created this PR to fix one or more vulnerable packages in the `pip` dependencies of this project.

Changes included in this PR

• Changes to the following files to upgrade the vulnerable dependencies to a fixed version:
  • requirements.txt

⚠️ Warning

tabulator 1.53.5 has requirement openpyxl>=2.6, but you have openpyxl 2.4.8.
social-auth-core 4.0.3 requires PyJWT, which is not installed.
s3transfer 0.4.2 requires botocore, which is not installed.
reportlab 3.5.55 requires pillow, which is not installed.
jsontableschema 0.10.1 requires jsonschema, which is not installed.
django-braces 1.15.0 has requirement Django>=2.2, but you have Django 1.11.29.
datapackage 0.8.1 requires jsonschema, which is not installed.
coveralls 1.1 requires coverage, which is not installed.
boto3 1.17.112 requires botocore, which is not installed.

Vulnerabilities that will be fixed

By pinning:

Severity	Priority Score (*)	Issue	Upgrade	Breaking Change	Exploit Maturity
	529/1000 Why? Has a fix available, CVSS 6.3	Cross-site Scripting (XSS) SNYK-PYTHON-DJANGORESTFRAMEWORK-1090569	djangorestframework: 3.5.0 -> 3.11.2	No	No Known Exploit
	449/1000 Why? Has a fix available, CVSS 4.7	Cross-site Scripting (XSS) SNYK-PYTHON-DJANGORESTFRAMEWORK-450194	djangorestframework: 3.5.0 -> 3.11.2	No	No Known Exploit
	646/1000 Why? Proof of Concept exploit, Has a fix available, CVSS 6.5	Server-side Request Forgery (SSRF) SNYK-PYTHON-REPORTLAB-1022145	reportlab: 3.5.26 -> 3.5.55	No	Proof of Concept
	696/1000 Why? Proof of Concept exploit, Has a fix available, CVSS 7.5	Remote Code Execution (RCE) SNYK-PYTHON-REPORTLAB-473444	reportlab: 3.5.26 -> 3.5.55	No	Proof of Concept

(*) Note that the real score may have changed since the PR was raised.

Some vulnerabilities couldn't be fully fixed and so Snyk will still find them when the project is tested again. This may be because the vulnerability existed within more than one direct dependency, but not all of the affected dependencies could be upgraded.

Check the changes in this PR to ensure they won't cause issues with your project.

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For more information:
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Learn how to fix vulnerabilities with free interactive lessons:

🦉 Cross-site Scripting (XSS)
🦉 Cross-site Scripting (XSS)
🦉 Server-side Request Forgery (SSRF)
🦉 More lessons are available in Snyk Learn

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This change is