Add Flake8 F4 Tests to .travis.yml (TheAlgorithms#974)

* Add Flake8 F4 Tests to .travis.yml

F4 tests check for import errors. Implements issue TheAlgorithms#973

* Remove wildcard imports

Author: PatOnTheBack

Diff for: .travis.yml

@@ -6,7 +6,7 @@ before_install: pip install --upgrade pip setuptools
 install: pip install -r requirements.txt
 before_script:
   - black --check . || true
-  - flake8 . --count --select=E9,F401,F63,F7,F82 --show-source --statistics
+  - flake8 . --count --select=E9,F4,F63,F7,F82 --show-source --statistics
 script:
   - scripts/validate_filenames.py  # no uppercase, no spaces, in a directory
   - mypy --ignore-missing-imports .

Diff for: linear_algebra/src/tests.py

@@ -9,7 +9,7 @@
 """
 
 import unittest
-from lib import *
+from lib import Matrix, Vector, axpy, squareZeroMatrix, unitBasisVector, zeroVector
 
 class Test(unittest.TestCase):
     def test_component(self):