Handling requests exceptions with friendly error messages

[yeisonvargasf]

This will add friendly error messages for the users of safety.

This covers requests exceptions: ConnectionError, Timeout and generic RequestException, also there is a handling for Bad HTTP codes with a custom message.

a few screenshots about how it looks:

[codecov[bot]]

Codecov Report

Merging #338 (593b50a) into master (d8609b9) will decrease coverage by 0.47%. The diff coverage is 67.85%.

@@            Coverage Diff             @@
##           master     #338      +/-   ##
==========================================
- Coverage   69.51%   69.03%   -0.48%     
==========================================
  Files           8        8              
  Lines         538      562      +24     
==========================================
+ Hits          374      388      +14     
- Misses        164      174      +10     

Impacted Files	Coverage Δ
safety/cli.py	52.45% <10.00%> (-4.18%)	:arrow_down:
safety/errors.py	100.00% <100.00%> (ø)
safety/safety.py	92.90% <100.00%> (-0.28%)	:arrow_down:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update d8609b9...593b50a. Read the comment docs.

[harlekeyn]

Yeison, could you please terminate all lines with a period?

For example: "Our engineers are working quickly to resolve the issue." instead of "Our engineers are working quickly to resolve the issue"

[yeisonvargasf]

"Our engineers are working quickly to resolve the issue"

Sure!