Update flake8 config to ignore W504, fix invalid escapes in v283 test

.flake8

@@ -10,4 +10,7 @@ exclude = .git,__pycache,node_modules
 #   E131: continuation line unaligned for hanging indent
 # - short variables should be avoided, but not currently enforced
 #   E741: do not use variables named ‘l’, ‘O’, or ‘I’
-ignore = E122, E126, E127, E128, E131, E741
+# - both W503 and W504 are enabled, but contradictory.
+#   code currently appears to adhere to W503.
+#   W504: line break after binary operator
+ignore = E122, E126, E127, E128, E131, E741, W504

test/imfv283_test/IMFV283Parser_test.py

@@ -7,9 +7,9 @@ from geomagio.imfv283 import IMFV283Parser, imfv283_codes
 
 
 IMFV283_EXAMPLE_VIC = '75C2A3A814023012741G43-1NN027EUP00191`A^P@RVxZ}|' + \
-    'D@@B_BEM@@@@@@@@@@@@@@@@@@@@@@@@@@@E|BxtTADVD@\E\BxxT@tVCh\\E' + \
-    'lByDT@xVCp\\EdBy@T@tVCh\EhByPT@xVCl\\EPBy@T@tVCd\EdBxlTA@VCp\\Eh' + \
-    'BxTTA@VCp\\EdBGxTA@VCl\EPBG`T@xVC\\\\DtBGHT@lVCD\DPBG@T@XVBh\\'
+    'D@@B_BEM@@@@@@@@@@@@@@@@@@@@@@@@@@@E|BxtTADVD@\\E\BxxT@tVCh\\E' + \
+    'lByDT@xVCp\\EdBy@T@tVCh\\EhByPT@xVCl\\EPBy@T@tVCd\\EdBxlTA@VCp\\Eh' + \
+    'BxTTA@VCp\\EdBGxTA@VCl\\EPBG`T@xVC\\\\DtBGHT@lVCD\DPBG@T@XVBh\\'
 
 IMFV283_EXAMPLE_FRD = '75C2102614023012927G43-0NN027EUP00191bx@WyhD{' + \
     'aDB~@X@{Bb@@@@@@@@@@@@@@@@@@@@@@@@@@@@[DAV[@cUAjT@[EAVZ@cUAjT@[' + \