Add flake8, mypy and isort setup

.flake8

@@ -0,0 +1,16 @@
+# vim: ft=dosini
+# https://flake8.pycqa.org/en/latest/user/configuration.html
+
+[flake8]
+# E131: continuation line unaligned for hanging indent
+# E301: when method is after a commented line + one blank line
+# E302: expected 2 blank lines, found 1 when using @dataclass
+# E303: more than one blank line between methods
+# W504: when line breaks occur after a binary operator
+# A003: when class attribute name is the same as a builtin
+# E402: when a module import isn't at the start of the file
+ignore = E131, E221, E241, E251, E301, E302, E303, W504, A003, E402
+
+max-complexity = 99
+inline-quotes  = "
+format = ${cyan}%(path)s${reset}:${yellow_bold}%(row)d${reset}:${green_bold}%(col)d${reset}: ${red_bold}%(code)s${reset} %(text)s

.isort.cfg

@@ -0,0 +1,5 @@
+# https://pycqa.github.io/isort/docs/configuration/options/
+
+[settings]
+multi_line_output      = 5
+include_trailing_comma = True

.mypy.ini

@@ -0,0 +1,10 @@
+# https://mypy.readthedocs.io/en/stable/config_file.html
+
+[mypy]
+cache_dir              = ~/.cache/mypy
+ignore_missing_imports = True
+follow_imports         = silent
+warn_redundant_casts   = True
+warn_unused_ignores    = True
+warn_unreachable       = True
+pretty                 = True

requirements-dev.txt

@@ -2,4 +2,16 @@ remote_pdb >= 2.0.0,  < 3
 pdbpp      >= 0.10.2, < 0.11
 pprintpp   >= 0.4.0,  < 0.5
 
+isort                 >= 5.6.4,  < 6
+mypy                  >= 0.790,  < 0.800
+flake8                >= 3.8.4,  < 4
+flake8-bugbear        >= 20.1.4, < 21
+flake8-commas         >= 2.0.0,  < 3
+flake8-comprehensions >= 3.3.0,  < 4
+flake8-executable     >= 2.0.4,  < 3
+flake8-logging-format >= 0.6.0,  < 0.7
+flake8-pie            >= 0.6.1,  < 0.7
+flake8-quotes         >= 3.2.0,  < 4
+flake8-colors         >= 0.1.6,  < 0.2
+
 git+http://github.com/mirukana/matrix-nio#egg=matrix-nio[e2e]