Merge pull request #8616 from cmonr/update-requests-module

Updated and pinned version for requests

Author: Cruz Monrreal

requirements.txt

@@ -6,7 +6,7 @@ intelhex>=1.3,<=2.2.1
 junit-xml==1.8
 pyYAML==3.13
 urllib3[secure]==1.23
-requests==2.19.1
+requests>=2.20,<2.21
 mbed-ls>=1.5.1,<1.7
 mbed-host-tests>=1.1.2,<=1.5
 mbed-greentea>=0.2.24,<=1.5