【Python】atomで「_tkinter.TclError: couldn't open .png: no such file or directory」と表示された場合の対処法

デスクトップ上に保存しているフォルダ内にある「.py」ファイルをatomで実行しようとしたところ、「_tkinter.TclError: couldn't open .png: no such file or directory」という表示が出ました。
「実行しようとしているファイル」と「開くことができないと言われているファイル」は、同じフォルダ内に配置しているのですが、何が原因なのでしょうか。
また、対処法についてもあわせてご教示ください。

利用環境は、Mac（ver. 10.13.2）,python3,atom(atom-runnerインストール済)

参考としてプログラムを以下に載せます

python
1import tkinter
2import random
3
4index = 0
5timer = 0
6score = 0
7tsugi = 0
8
9cursor_x = 0
10cursor_y = 0
11mouse_x = 0
12mouse_y = 0
13mouse_c = 0
14
15def mouse_move(e):
16    global mouse_x, mouse_y
17    mouse_x = e.x
18    mouse_y = e.y
19
20def mouse_press(e):
21    global mouse_c
22    mouse_c = 1
23
24neko = []
25check = []
26for i in range(10):
27    neko.append([0,0,0,0,0,0,0,0])
28    check.append([0,0,0,0,0,0,0,0])
29
30def draw_neko():
31    cvs.delete("NEKO")
32    for y in range(10):
33        for x in range(8):
34            if neko[y][x] > 0:
35                cvs.create_image(x*72+60, y*72+60, image=img_neko[neko[y][x]], tag="NEKO")
36
37def check_neko():
38    for y in range(10):
39        for x in range(8):
40            check[y][x] = neko[y][x]
41
42    for y in range(1, 9):
43        for x in range(8):
44            if check[y][x] > 0:
45                if check[y-1][x] == check[y][x] and check[y+1][x] == check[y][x]:
46                    neko[y-1][x] = 7
47                    neko[y][x] = 7
48                    neko[y+1][x] = 7
49
50    for y in range(10):
51        for x in range(1, 7):
52            if check[y][x] > 0:
53                if check[y][x-1] == check[y][x] and check[y][x+1] == check[y][x]:
54                    neko[y][x-1] = 7
55                    neko[y][x] = 7
56                    neko[y][x+1] = 7
57
58    for y in range(1, 9):
59        for x in range(1, 7):
60            if check[y][x] > 0:
61                if check[y-1][x-1] == check[y][x] and check[y+1][x+1] == check[y][x]:
62                    neko[y-1][x-1] = 7
63                    neko[y][x] = 7
64                    neko[y+1][x+1] = 7
65                if check[y-1][x+1] == check[y][x] and check[y+1][x-1] == check[y][x]:
66                    neko[y-1][x+1] = 7
67                    neko[y][x] = 7
68                    neko[y+1][x-1] = 7
69
70def sweep_neko():
71    num = 0
72    for y in range(10):
73        for x in range(8):
74            if neko[y][x] == 7:
75                neko[y][x] = 0
76                num = num + 1
77    return num
78
79def drop_neko():
80    flg = False
81    for y in range(8, -1, -1):
82        for x in range(8):
83            if neko[y][x] != 0 and neko[y+1][x] == 0:
84                neko[y+1][x] = neko[y][x]
85                neko[y][x] = 0
86                flg = True
87    return flg
88
89def over_neko():
90    for x in range(8):
91        if neko[0][x] > 0:
92            return True
93    return False
94
95def set_neko():
96    for x in range(8):
97        neko[0][x] = random.randint(0, 6)
98
99def draw_txt(txt, x, y, siz, col, tg):
100    fnt = ("Times New Roman", siz, "bold")
101    cvs.create_text(x+2, y+2, text=txt, fill="black", font=fnt, tag=tg)
102    cvs.create_text(x, y, text=txt, fill=col, font=fnt, tag=tg)
103
104def game_main():
105    global index, timer, score, tsugi
106    global cursor_x, cursor_y, mouse_c
107    if index == 0: # タイトルロゴ
108        draw_txt("ねこねこ", 312, 240, 100, "violet", "TITLE")
109        draw_txt("Click to start.", 312, 560, 50, "orange", "TITLE")
110        index = 1
111        mouse_c = 0
112    elif index == 1: # タイトル画面　スタート待ち
113        if mouse_c == 1:
114            for y in range(10):
115                for x in range(8):
116                    neko[y][x] = 0
117            mouse_c = 0
118            score = 0
119            tsugi = 0
120            cursor_x = 0
121            cursor_y = 0
122            set_neko()
123            draw_neko()
124            cvs.delete("TITLE")
125            index = 2
126    elif index == 2: #　落下
127        if drop_neko() == False:
128            index = 3
129        draw_neko()
130    elif index == 3: #　揃ったか
131        check_neko()
132        draw_neko()
133        index = 4
134    elif index == 4: #　揃ったネコがあれば消す
135        sc = sweep_neko()
136        score = score + sc*10
137        if sc > 0:
138            index = 2
139        else:
140            if over_neko() == False:
141                tsugi = random.randint(1,6)
142                index = 5
143            else:
144                index = 6
145                timer = 0
146        draw_neko()
147    elif index == 5: #マウス入力を待つ
148        if 24 <= mouse_x and mouse_x < 24+72*8 and 24 <= mouse_y and mouse_y < 24+72*10:
149            cursor_x = int((mouse_x-24)/72)
150            cursor_y = int((mouse_y-24)/72)
151            if mouse_c == 1:
152                mouse_c = 0
153                set_neko()
154                neko[cursor_y][cursor_x] = tsugi
155                tsugi = 0
156                index = 2
157        cvs.delete("CURSOR")
158        cvs.create_image(cursor_x*72+60, cursor_y*72+60, image=cursor, tag="CURSOR")
159        draw_neko()
160    elif index == 6: # ゲームオーバー
161        timer = timer + 1
162        if timer == 1:
163            draw_txt("GAME OVER", 312, 348, 60, "red", "OVER")
164        if timer ==50:
165            cvs.delete("OVER")
166            index = 0
167    cvs.delete("INFO")
168    draw_txt("SCORE "+str(score), 160, 60, 32, "blue", "INFO")
169    if tsugi > 0:
170        cvs.create_image(752, 128, image=img_neko[tsugi], tag="INFO")
171    root.after(100, game_main)
172
173root = tkinter.Tk()
174root.title("落ち物バズル「ねこねこ」")
175root.resizable(False, False)
176root.bind("<Motion>", mouse_move)
177root.bind("<ButtonPress>", mouse_press)
178cvs = tkinter.Canvas(root, width=912, height=768)
179cvs.pack()
180
181bg = tkinter.PhotoImage(file="neko_bg.png")
182cursor = tkinter.PhotoImage(file="neko_cursor.png")
183img_neko = [
184    None,
185    tkinter.PhotoImage(file="neko1.png"),
186    tkinter.PhotoImage(file="neko2.png"),
187    tkinter.PhotoImage(file="neko3.png"),
188    tkinter.PhotoImage(file="neko4.png"),
189    tkinter.PhotoImage(file="neko5.png"),
190    tkinter.PhotoImage(file="neko6.png"),
191    tkinter.PhotoImage(file="neko_niku.png")
192    ]
193
194cvs.create_image(456, 384, image=bg)
195game_main()
196root.mainloop()
197