#10 - improve config and Python style

N816 actually highlighted a problem, not to be ignored.  Rather than have config export variable that's not a constant, move that variable into a function for checking the rest of the config.

config.py

@@ -9,21 +9,32 @@
 CANVAS_BASE_URL: str = os.getenv('CANVAS_BASE_URL')
 CANVAS_API_TOKEN: str = os.getenv('CANVAS_API_TOKEN')
 COURSE_IDS_CSV: str = os.getenv('COURSE_IDS_CSV')
+COURSE_IDS: List[str] = [
+    c.strip() for c in COURSE_IDS_CSV.split(',') if c
+] if COURSE_IDS_CSV else None
 
-envErrors = []
 
-if CANVAS_BASE_URL is None:
-    envErrors.append('CANVAS_BASE_URL')
+def checkConfig():
+    envErrors = []
 
-if CANVAS_API_TOKEN is None:
-    envErrors.append('CANVAS_API_TOKEN')
+    if CANVAS_BASE_URL is None:
+        envErrors.append('CANVAS_BASE_URL')
 
-if COURSE_IDS_CSV is None:
-    envErrors.append('COURSE_IDS_CSV')
+    if CANVAS_API_TOKEN is None:
+        envErrors.append('CANVAS_API_TOKEN')
 
-if len(envErrors) > 0:
-    LOGGER.critical('The following environment variable(s) are not set: '
-                    f'{", ".join(envErrors)}')
-    sys.exit()
+    if COURSE_IDS_CSV is None:
+        envErrors.append('COURSE_IDS_CSV')
 
-COURSE_IDS: List[str] = [c.strip() for c in COURSE_IDS_CSV.split(',')]
+    if len(envErrors) > 0:
+        LOGGER.critical('The following environment variable(s) are not set: '
+                        f'{", ".join(envErrors)}')
+        sys.exit()
+
+    if COURSE_IDS is None:
+        LOGGER.critical('COURSE_IDS could not be set. '
+                        '(Problem parsing COURSE_IDS_CSV?)')
+        sys.exit()
+
+
+checkConfig()

setup.cfg

@@ -1,6 +1,6 @@
 [flake8]
+# Vive la résistance!  Vive la mixedCase!
 # N802 function name '…' should be lowercase
 # N803 argument name '…' should be lowercase
 # N806 variable '…' in function should be lowercase
-# N816 variable '…' in global scope should not be mixedCase
-extend-ignore = N802,N803,N806,N816
+extend-ignore = N802,N803,N806