Add gui entrypoint.

setup.py

@@ -44,8 +44,8 @@ with open("README.md", "r") as fh:
 name = 'pymagglobal'
 version = get_version('pymagglobal/__init__.py')
 description = '''python interface for global geomagnetic field models '''
-copyright = f'2020 Helmholtz Centre Potsdam GFZ, ' \
-    + f'German Research Centre for Geosciences, Potsdam, Germany'
+copyright = '2020 Helmholtz Centre Potsdam GFZ, ' \
+    + 'German Research Centre for Geosciences, Potsdam, Germany'
 
 
 setuptools.setup(
@@ -66,6 +66,8 @@ setuptools.setup(
     extras_require={'tests': ['orthopoly>=0.9', 'packaging']},
     package_data={'pymagglobal': ['dat/*']},
     include_package_data=True,
-    entry_points={'console_scripts': [f'pymagglobal = '
-                                      f'pymagglobal.__main__:main']},
+    entry_points={'console_scripts': ['pymagglobal = '
+                                      'pymagglobal.__main__:main',
+                                      'pymagglobal-gui = '
+                                      'pymagglobal.GUI:main']},
 )